Jose Vergara - Academia.edu (original) (raw)

Papers by Jose Vergara

Aquaculture, 2002

... than proportionally. This can be explained because of the particular discontinuities presente... more ... than proportionally. This can be explained because of the particular discontinuities presented in the size of technical equipments, such as classification machines, service boats, and cages (Hill and Ingersent, 1982). The largest ...

Estuarine Coastal and Shelf Science, 2005

The use of morphometric variations as acclimation mechanisms was tested in natural populations of... more The use of morphometric variations as acclimation mechanisms was tested in natural populations of the intertidal seagrass Zostera noltii in Ria Formosa (Algarve, southern Portugal). To achieve the objective, two populations of Z. noltii were studied; a bed exposed and physically impacted by the artificial opening of a new inlet, and a second bed protected from dynamic impacts. At each meadow, morphometry and other plant-key variables such as tissue composition, photosynthetic parameters and dynamic properties (i.e. modules and whole plant growth rates) were monitored. After severe physical impacts in winter 1998, the newly appeared plants in the exposed meadow showed permanent morphometric changes. This new morphotype (small-leaved morphotype, SLM) had shorter (65%) and narrower leaves (25%) with longer internodes (4 times), than the large-leaved morphotype (LLM) found in the protected meadow or in the exposed meadow prior to the large disturbance. The SLM also had a larger non-photosynthetic biomass fraction, but increased photosynthetic capacity compared with the LLM. The morphometric and physiological changes were related to the fast recovery (<6 months) exhibited in the exposed meadow. In the protected meadow, morphometric changes (minor and short term) were associated with seasonal patterns. After the recovery, exposed and protected meadows gave similar production estimates supporting the hypothesis that a new stable state had been established in the exposed meadow. From these results, it can be concluded that Z. noltii has a remarkable phenotypic plasticity supported by coordinated changes in dynamic variables (i.e. leaf and internodal elongation rates and plastochrone index). Phenotypic plasticity seems to be the main mechanism by which this species is able to cope with short and long term environmental changes.

Marine Biology, 1996

The red algaGelidium sesquipedale (Clem.) Born. et Thur. has been cultured in chemostats to asses... more The red algaGelidium sesquipedale (Clem.) Born. et Thur. has been cultured in chemostats to assess the effects of light quality and photon-fluence rate (PFR) on growth, photosynthesis and biochemical composition. Plants under blue and red light (BL and RL) showed higher growth rates than under white light (WL) of the same PFR (40 μmol m−2 s−1). The light-saturated rate of photosynthesis was higher for algae grown under BL and RL than for algae grown under WL. When algae were transferred to WL of moderate PFR (100 μmol m−2 s−1), the light-saturated rate of photosynthesis decreased, being higher in previously RL-grown algae than in previously BL- and WL-grown algae. The initial slope of photosynthesis-irradiance (PI) curves (α) was affected by PFR but not by light quality. Pigment content was little affected by light quality. Light-quality treatments also affected the biochemical composition of the alga; previous exposure to various light treatments activate or repress several metabolical pathways that are fully expressed in the subsequent phase of WL of moderate PFR. Thus, phycobiliproteins and soluble proteins increased for previously BL- and RL-grown algae, whereas insoluble carbohydrate concentration was reduced, indicating a change of the C-partitioning between carbon compounds and organic nitrogen compounds. Inorganic nitrogen metabolism was also affected by light: under WL of moderate PFR, NO3− was totally depleted from sea water, and maximal values of NO3− uptake were recorded. In addition, neither NO2− nor NH4+ was released. However, when algae were transferred to a low PFR, there was a drastic reduction of NO3− uptake under WL, which only partially recovered over time. It was accompanied by the release of NO2−, but not NH4+, to the culture medium. Under BL and RL, however, there was a transient enhancement of NO3− uptake that was followed by a net release of NO2− and NH4−. Growth rates were not correlated with PFR. This could be due to the the dynamics of internal carbon mobilization and accumulation in the algae. When algae were exposed to a moderate PFR of WL, carbon requirements for growth were satisfied by photosynthesis. Thus, there was a net accumulation of carbon in the tissue. In contrast, when algae were exposed to low PFRs of either WL, BL or RL, observed growth rates could not be maintained by photosynthesis and carbon was mobilized.

Journal of Experimental Marine Biology and Ecology, 2002

Journal of Applied Phycology, 2002

Three estuarine macroalgae (Ulva rotundata,Enteromorpha intestinalis, Gracilariagracilis) of econ... more Three estuarine macroalgae (Ulva rotundata,Enteromorpha intestinalis, Gracilariagracilis) of economic potential were cultivated in the laboratory toassess their biofiltering capacities for ammonium in waste effluents from a seabass (Dicentrarchus labrax) cultivation tank. The studywasdeveloped to investigate the functioning of N nutrition of the three species.Atlow water flow (< 2 volumes d−1) the three species strippedefficiently the ammonium dissolved in the waste water from the fish tank, withaminimum biofiltering efficiency estimate of 61% in unstarved cultures ofG. gracilis at a water flow of 2 volumesd−1. Maximum velocity for ammonium uptake (89.0 μmolNH4+ g−1 dry wth−1) was found in U. rotundata,whereas G. gracilis showed the highest affinity for thisnutrient. The net ammonium uptake rate was significantly affected by the waterflow, being greatest at the highest flow assayed (2 volumesd−1). Variations of tissue N and C:N ratios during aflow-through experiment suggested that N was not limiting macroalgal growth.However, when ammonium was supplied at a flow rate of 0.5 volumesd−1, specially in a three-stage design, the marked reductionintissue N and the biomass C:N:P ratios suggested a more general nutrientdeficiency. A significant correlation was found between growth rates and the Nbiomass gained in the cultures. The three-stage design under low water flow(0.5volumes d−1) showed that the highest ammonium uptake rates (upto 80.9 μmol NH4+ g−1 dry wtd−1 in U. rotundata) were found inthe first stage, with decreasing rates in the following ones. As a result, lowincrements or even losses of total N biomass in these stages were found,suggesting that ammonium was excreted from the algae. We conclude that thesespecies present a potential ability to biofilter the ammonium dissolved inwastewater from a D. labrax cultivation tank, suggesting thatscaling up the biofiltration designs, future practises using these macroalgaemay be implemented in the local fish farms, resulting in both environmental andeconomical advantages.

Journal of Applied Phycology, 2002

The potential of three estuarine macroalgae (Ulvarotundata, Enteromorpa intestinalis andGracilari... more The potential of three estuarine macroalgae (Ulvarotundata, Enteromorpa intestinalis andGracilaria gracilis) as biofilters for phosphate ineffluents of a sea bass (Dicentrarchus labrax) cultivationtank was studied. These seaweeds thrive in Cádiz Bay and were alsoselected because of their economic potential, so that environmental andeconomicadvantages may be achieved by future integrated aquaculture practices in thelocal fish farms. The study was designed to investigate the functioning of Pnutrition of the selected species. Maximum velocity of phosphate uptake (2.86μmol PO4 g−1 dry wth−1) was found in U. rotundata.This species also showed the highest affinity for this nutrient. At low flowrates (< 2 volumes d−1), the three species efficientlyfiltered the phosphate dissolved in the waste water, with a minimum efficiencyof 60.7% in U. rotundata. Net phosphate uptake rate wassignificantly affected by the water flow, being greatest at the highest rateassayed (2 volumes d−1). The marked decrease in tissue P shownby the three species during a flow-through experiment suggested that growth wasP limited. However, due to the increase in biomass, total P biomass increasedinthe cultures. A significant correlation was found between growth rates and thenet P biomass gained in the cultures. A three-stage design under low water flow(0.5 volumes d−1) showed that the highest growth rates (up to0.14 d−1) and integrated phosphate uptake rates(up to 5.8 μmol PO43− g−1dry wt d−1) were found in E.intestinalis in the first stage, with decreasing rates in thefollowing ones. As a result, phosphate become limiting and low increments oreven losses of total P biomass in these stages were found suggesting thatphosphate was excreted from the algae. The results show the potential abilityofthe three species to reduce substantially, at low water flow, the phosphateconcentration in waste waters from a D. labrax cultivationtank, and thus the quality of effluents from intensive aquaculture practices.

Estuarine Coastal and Shelf Science, 2005

Marine Biology, 1996

The red algaGelidium sesquipedale (Clem.) Born. et Thur. has been cultured in chemostats to asses... more The red algaGelidium sesquipedale (Clem.) Born. et Thur. has been cultured in chemostats to assess the effects of light quality and photon-fluence rate (PFR) on growth, photosynthesis and biochemical composition. Plants under blue and red light (BL and RL) showed higher growth rates than under white light (WL) of the same PFR (40 μmol m−2 s−1). The light-saturated rate of photosynthesis was higher for algae grown under BL and RL than for algae grown under WL. When algae were transferred to WL of moderate PFR (100 μmol m−2 s−1), the light-saturated rate of photosynthesis decreased, being higher in previously RL-grown algae than in previously BL- and WL-grown algae. The initial slope of photosynthesis-irradiance (PI) curves (α) was affected by PFR but not by light quality. Pigment content was little affected by light quality. Light-quality treatments also affected the biochemical composition of the alga; previous exposure to various light treatments activate or repress several metabolical pathways that are fully expressed in the subsequent phase of WL of moderate PFR. Thus, phycobiliproteins and soluble proteins increased for previously BL- and RL-grown algae, whereas insoluble carbohydrate concentration was reduced, indicating a change of the C-partitioning between carbon compounds and organic nitrogen compounds. Inorganic nitrogen metabolism was also affected by light: under WL of moderate PFR, NO3− was totally depleted from sea water, and maximal values of NO3− uptake were recorded. In addition, neither NO2− nor NH4+ was released. However, when algae were transferred to a low PFR, there was a drastic reduction of NO3− uptake under WL, which only partially recovered over time. It was accompanied by the release of NO2−, but not NH4+, to the culture medium. Under BL and RL, however, there was a transient enhancement of NO3− uptake that was followed by a net release of NO2− and NH4−. Growth rates were not correlated with PFR. This could be due to the the dynamics of internal carbon mobilization and accumulation in the algae. When algae were exposed to a moderate PFR of WL, carbon requirements for growth were satisfied by photosynthesis. Thus, there was a net accumulation of carbon in the tissue. In contrast, when algae were exposed to low PFRs of either WL, BL or RL, observed growth rates could not be maintained by photosynthesis and carbon was mobilized.

Journal of Experimental Marine Biology and Ecology, 2002

Journal of Applied Phycology, 2002

Three estuarine macroalgae (Ulva rotundata,Enteromorpha intestinalis, Gracilariagracilis) of econ... more Three estuarine macroalgae (Ulva rotundata,Enteromorpha intestinalis, Gracilariagracilis) of economic potential were cultivated in the laboratory toassess their biofiltering capacities for ammonium in waste effluents from a seabass (Dicentrarchus labrax) cultivation tank. The studywasdeveloped to investigate the functioning of N nutrition of the three species.Atlow water flow (< 2 volumes d−1) the three species strippedefficiently the ammonium dissolved in the waste water from the fish tank, withaminimum biofiltering efficiency estimate of 61% in unstarved cultures ofG. gracilis at a water flow of 2 volumesd−1. Maximum velocity for ammonium uptake (89.0 μmolNH4+ g−1 dry wth−1) was found in U. rotundata,whereas G. gracilis showed the highest affinity for thisnutrient. The net ammonium uptake rate was significantly affected by the waterflow, being greatest at the highest flow assayed (2 volumesd−1). Variations of tissue N and C:N ratios during aflow-through experiment suggested that N was not limiting macroalgal growth.However, when ammonium was supplied at a flow rate of 0.5 volumesd−1, specially in a three-stage design, the marked reductionintissue N and the biomass C:N:P ratios suggested a more general nutrientdeficiency. A significant correlation was found between growth rates and the Nbiomass gained in the cultures. The three-stage design under low water flow(0.5volumes d−1) showed that the highest ammonium uptake rates (upto 80.9 μmol NH4+ g−1 dry wtd−1 in U. rotundata) were found inthe first stage, with decreasing rates in the following ones. As a result, lowincrements or even losses of total N biomass in these stages were found,suggesting that ammonium was excreted from the algae. We conclude that thesespecies present a potential ability to biofilter the ammonium dissolved inwastewater from a D. labrax cultivation tank, suggesting thatscaling up the biofiltration designs, future practises using these macroalgaemay be implemented in the local fish farms, resulting in both environmental andeconomical advantages.

Journal of Applied Phycology, 2002

The potential of three estuarine macroalgae (Ulvarotundata, Enteromorpa intestinalis andGracilari... more The potential of three estuarine macroalgae (Ulvarotundata, Enteromorpa intestinalis andGracilaria gracilis) as biofilters for phosphate ineffluents of a sea bass (Dicentrarchus labrax) cultivationtank was studied. These seaweeds thrive in Cádiz Bay and were alsoselected because of their economic potential, so that environmental andeconomicadvantages may be achieved by future integrated aquaculture practices in thelocal fish farms. The study was designed to investigate the functioning of Pnutrition of the selected species. Maximum velocity of phosphate uptake (2.86μmol PO4 g−1 dry wth−1) was found in U. rotundata.This species also showed the highest affinity for this nutrient. At low flowrates (< 2 volumes d−1), the three species efficientlyfiltered the phosphate dissolved in the waste water, with a minimum efficiencyof 60.7% in U. rotundata. Net phosphate uptake rate wassignificantly affected by the water flow, being greatest at the highest rateassayed (2 volumes d−1). The marked decrease in tissue P shownby the three species during a flow-through experiment suggested that growth wasP limited. However, due to the increase in biomass, total P biomass increasedinthe cultures. A significant correlation was found between growth rates and thenet P biomass gained in the cultures. A three-stage design under low water flow(0.5 volumes d−1) showed that the highest growth rates (up to0.14 d−1) and integrated phosphate uptake rates(up to 5.8 μmol PO43− g−1dry wt d−1) were found in E.intestinalis in the first stage, with decreasing rates in thefollowing ones. As a result, phosphate become limiting and low increments oreven losses of total P biomass in these stages were found suggesting thatphosphate was excreted from the algae. The results show the potential abilityofthe three species to reduce substantially, at low water flow, the phosphateconcentration in waste waters from a D. labrax cultivationtank, and thus the quality of effluents from intensive aquaculture practices.

Aquaculture, 1995

... The increase in lipid deposition in muscle and liver, as well as the decrease in liver glycog... more ... The increase in lipid deposition in muscle and liver, as well as the decrease in liver glycogen, have been reported as signs of P deficiency in fish (Sakamoto and Yone, 1978). ... Food Chem., 32: 5967. Sakamoto, S. and Yone, Y., 1978. ...

Aquaculture, 1994

Pink dentex (D. gibbosus) can be considered as a potential candidate to diversify the culture of ... more Pink dentex (D. gibbosus) can be considered as a potential candidate to diversify the culture of Sparidae, due both to the importance of dentex fisheries and market within Europe, and to its phylogenetic closeness to the gilthead sea bream (Sparus aurata, Linnaeus, 1758). First trials to obtain D. gibbosus spawnings under captive conditions were carried out at the Planta Experimental de Cultivos Marinos (Instituto Canario de Ciencias Marinas, Gran Canaria, Canary Islands, Spain) in May, 1991. Broodstock management conditions determining egg quality, embryonic and larval development of D. gibbosus up to day 31 are described for the first time. Larval allometric characteristics were studied. The equation y=2.321×e0.03975x represents larval growth under experimental conditions. A comparison of egg size, hatching time and size of newly hatched larvae in several Sparidae under culture conditions is also presented. Results on broodstock acclimation, natural spawnings and larval growth rates suggest that pink dentex has a high potential for commercial culture.

Fish Physiology and Biochemistry, 2001

The aim of the present study was to determine the combined effect of both stress and EFA deficien... more The aim of the present study was to determine the combined effect of both stress and EFA deficiency on several biological and biochemical parameters. Fish were fed during 15 weeks two isocaloric and isoproteic diets: a control diet based on fish oil and formulated to meet the n-3 HUFA requirements for this species (1.5% of n-3 HUFA) and a deficient diet containing beef tallow and formulated to be deficient in n-3 HUFA. Each experimental diet was evaluated both at high and low stocking densities (10 and 3.2 kg m−3 of initial density, respectively). High stocking density produced a chronic stress situation with elevation of plasma cortisol levels. It also caused a reduction in hepatosomatic index and liver lipid contents, increasing the oleic acid/n-3 HUFA ratios in the polar lipids. Fish fed the EFA deficient diet at low stocking density showed common deficiency symptoms. High stocking density in fish fed the EFA deficient diet induced a higher degree of EFA deficiency symptoms leading to mortality, liver steatosis, liver lipid deposition, reduced muscle lipid and reduced n-3 HUFA contents, which particularly affected EPA, but not DHA, suggesting a preferential retention of the latter fatty acid, specially in the phosphoglycerides fraction.

Fish Physiology and Biochemistry, 1999

High stocking density has been shown to produce a wide variety of effects on cultured fish popula... more High stocking density has been shown to produce a wide variety of effects on cultured fish populations, such as alterations in behavior and poor feed utilization, resulting in mortality and poor growth. High stocking density has also been reported to produce chronic stress and mobilization of energy sources in fish. There are few studies focusing on the effect of high stocking density on one of the most important marine fish species for Mediterranean aquaculture, gilthead seabream (Sparus aurata). Consequently, this study investigates the effect of high stocking density on juveniles of this species, focusing on effects of stocking density on growth, biochemical composition, immune status and hematology. The results of this study showed that high stocking density produced a chronic stress situation. Plasma cortisol levels increased up to 16.25 ng ml−1 in fish held at high stocking; this value was 4 fold that of fish held at low stocking; density (3.91 ng ml−1 ). As a consequenceof this stressful situation, there was both haemoconcentration and a decrease in alternative complement pathway (ACP), an important component of the immune system of fish (from 167.23 U ml−1 down to 146.37 U ml−1). Haematocrit, haemoglobin concentration and red blood cell count were significantly higher in fish held at high stocking density (43.87%, 10.76 9dl−1 and 3.36 ×106 mm−3, respectively) compared with those fish held at low stocking density (37.21%, 9.32 g/dlg−1 and 2.82 ×106 mm−3, respectively). In addition, high stocking density produced a decrease in hepatosomatic index (from 2.26 down to 2.04) and altered liver fatty acid composition. Oleic acid (18: 1n-9) decreased in liver total lipids of fish held at high stocking density and arachidonic acid (20: 4-n6) and n-3 high unsaturated fatty acids (n-3 HUFA) were reduced in liver polar lipids of those fish. These alterations reflect the effect of stocking density on lipid metabolism to help meet the increased energy demand.

Aquaculture, 1999

High stocking density is an aquaculture-related situation which causes crowding stress in fish an... more High stocking density is an aquaculture-related situation which causes crowding stress in fish and potentially affecting the immune system. Protection against disease can be induced through immunostimulation, enhancing defence mechanisms. Vitamins C and E are among the most important nutrients influencing the immune system, although the effect of these vitamins in the amelioration of stress in fish has not been studied in detail. An experiment was carried out to study the effect dietary supplementation of vitamin C or vitamin E on the immune system of fish under a crowding stress situation in a commercial farm. A commercial diet for this species was supplemented with vitamin C or vitamin E and these diets were assayed at high stocking density (over 40 kg m−3) and the results were compared with those from fish fed the commercial diet and held at farm conditions (20 kg m−3). Some biological and immunological parameters were studied at the end of the experimental period. Fish held at high stocking density showed lower final weight than fish held at lower stocking density. These also showed higher plasma cortisol levels (over 6 ng cortisol ml−1 plasma for all the diets assayed) than those fish held at lower density (1.13 ng cortisol ml−1 plasma). High stocking density produced higher serum lysozyme activity values in fish fed the commercial diet compared with those fish held at lower density (67.49 and 36.84 units ml−1, respectively). This effect was not observed in fish held at high stocking density but fed vitamin C and vitamin E supplemented diets (lysozyme activity: 21.97 and 19.71 units ml−1, respectively). High stocking density also appeared to decrease serum alternative complement activity. In those fish fed the vitamin E supplemented diet, levels were similar to fish held at low stocking density, suggesting the role of this vitamin in this defense mechanism.

Ecological Modelling, 2003

Aquaculture, 2002

... than proportionally. This can be explained because of the particular discontinuities presente... more ... than proportionally. This can be explained because of the particular discontinuities presented in the size of technical equipments, such as classification machines, service boats, and cages (Hill and Ingersent, 1982). The largest ...

Estuarine Coastal and Shelf Science, 2005

The use of morphometric variations as acclimation mechanisms was tested in natural populations of... more The use of morphometric variations as acclimation mechanisms was tested in natural populations of the intertidal seagrass Zostera noltii in Ria Formosa (Algarve, southern Portugal). To achieve the objective, two populations of Z. noltii were studied; a bed exposed and physically impacted by the artificial opening of a new inlet, and a second bed protected from dynamic impacts. At each meadow, morphometry and other plant-key variables such as tissue composition, photosynthetic parameters and dynamic properties (i.e. modules and whole plant growth rates) were monitored. After severe physical impacts in winter 1998, the newly appeared plants in the exposed meadow showed permanent morphometric changes. This new morphotype (small-leaved morphotype, SLM) had shorter (65%) and narrower leaves (25%) with longer internodes (4 times), than the large-leaved morphotype (LLM) found in the protected meadow or in the exposed meadow prior to the large disturbance. The SLM also had a larger non-photosynthetic biomass fraction, but increased photosynthetic capacity compared with the LLM. The morphometric and physiological changes were related to the fast recovery (<6 months) exhibited in the exposed meadow. In the protected meadow, morphometric changes (minor and short term) were associated with seasonal patterns. After the recovery, exposed and protected meadows gave similar production estimates supporting the hypothesis that a new stable state had been established in the exposed meadow. From these results, it can be concluded that Z. noltii has a remarkable phenotypic plasticity supported by coordinated changes in dynamic variables (i.e. leaf and internodal elongation rates and plastochrone index). Phenotypic plasticity seems to be the main mechanism by which this species is able to cope with short and long term environmental changes.

Marine Biology, 1996

The red algaGelidium sesquipedale (Clem.) Born. et Thur. has been cultured in chemostats to asses... more The red algaGelidium sesquipedale (Clem.) Born. et Thur. has been cultured in chemostats to assess the effects of light quality and photon-fluence rate (PFR) on growth, photosynthesis and biochemical composition. Plants under blue and red light (BL and RL) showed higher growth rates than under white light (WL) of the same PFR (40 μmol m−2 s−1). The light-saturated rate of photosynthesis was higher for algae grown under BL and RL than for algae grown under WL. When algae were transferred to WL of moderate PFR (100 μmol m−2 s−1), the light-saturated rate of photosynthesis decreased, being higher in previously RL-grown algae than in previously BL- and WL-grown algae. The initial slope of photosynthesis-irradiance (PI) curves (α) was affected by PFR but not by light quality. Pigment content was little affected by light quality. Light-quality treatments also affected the biochemical composition of the alga; previous exposure to various light treatments activate or repress several metabolical pathways that are fully expressed in the subsequent phase of WL of moderate PFR. Thus, phycobiliproteins and soluble proteins increased for previously BL- and RL-grown algae, whereas insoluble carbohydrate concentration was reduced, indicating a change of the C-partitioning between carbon compounds and organic nitrogen compounds. Inorganic nitrogen metabolism was also affected by light: under WL of moderate PFR, NO3− was totally depleted from sea water, and maximal values of NO3− uptake were recorded. In addition, neither NO2− nor NH4+ was released. However, when algae were transferred to a low PFR, there was a drastic reduction of NO3− uptake under WL, which only partially recovered over time. It was accompanied by the release of NO2−, but not NH4+, to the culture medium. Under BL and RL, however, there was a transient enhancement of NO3− uptake that was followed by a net release of NO2− and NH4−. Growth rates were not correlated with PFR. This could be due to the the dynamics of internal carbon mobilization and accumulation in the algae. When algae were exposed to a moderate PFR of WL, carbon requirements for growth were satisfied by photosynthesis. Thus, there was a net accumulation of carbon in the tissue. In contrast, when algae were exposed to low PFRs of either WL, BL or RL, observed growth rates could not be maintained by photosynthesis and carbon was mobilized.

Journal of Experimental Marine Biology and Ecology, 2002

Journal of Applied Phycology, 2002

Three estuarine macroalgae (Ulva rotundata,Enteromorpha intestinalis, Gracilariagracilis) of econ... more Three estuarine macroalgae (Ulva rotundata,Enteromorpha intestinalis, Gracilariagracilis) of economic potential were cultivated in the laboratory toassess their biofiltering capacities for ammonium in waste effluents from a seabass (Dicentrarchus labrax) cultivation tank. The studywasdeveloped to investigate the functioning of N nutrition of the three species.Atlow water flow (< 2 volumes d−1) the three species strippedefficiently the ammonium dissolved in the waste water from the fish tank, withaminimum biofiltering efficiency estimate of 61% in unstarved cultures ofG. gracilis at a water flow of 2 volumesd−1. Maximum velocity for ammonium uptake (89.0 μmolNH4+ g−1 dry wth−1) was found in U. rotundata,whereas G. gracilis showed the highest affinity for thisnutrient. The net ammonium uptake rate was significantly affected by the waterflow, being greatest at the highest flow assayed (2 volumesd−1). Variations of tissue N and C:N ratios during aflow-through experiment suggested that N was not limiting macroalgal growth.However, when ammonium was supplied at a flow rate of 0.5 volumesd−1, specially in a three-stage design, the marked reductionintissue N and the biomass C:N:P ratios suggested a more general nutrientdeficiency. A significant correlation was found between growth rates and the Nbiomass gained in the cultures. The three-stage design under low water flow(0.5volumes d−1) showed that the highest ammonium uptake rates (upto 80.9 μmol NH4+ g−1 dry wtd−1 in U. rotundata) were found inthe first stage, with decreasing rates in the following ones. As a result, lowincrements or even losses of total N biomass in these stages were found,suggesting that ammonium was excreted from the algae. We conclude that thesespecies present a potential ability to biofilter the ammonium dissolved inwastewater from a D. labrax cultivation tank, suggesting thatscaling up the biofiltration designs, future practises using these macroalgaemay be implemented in the local fish farms, resulting in both environmental andeconomical advantages.

Journal of Applied Phycology, 2002

The potential of three estuarine macroalgae (Ulvarotundata, Enteromorpa intestinalis andGracilari... more The potential of three estuarine macroalgae (Ulvarotundata, Enteromorpa intestinalis andGracilaria gracilis) as biofilters for phosphate ineffluents of a sea bass (Dicentrarchus labrax) cultivationtank was studied. These seaweeds thrive in Cádiz Bay and were alsoselected because of their economic potential, so that environmental andeconomicadvantages may be achieved by future integrated aquaculture practices in thelocal fish farms. The study was designed to investigate the functioning of Pnutrition of the selected species. Maximum velocity of phosphate uptake (2.86μmol PO4 g−1 dry wth−1) was found in U. rotundata.This species also showed the highest affinity for this nutrient. At low flowrates (< 2 volumes d−1), the three species efficientlyfiltered the phosphate dissolved in the waste water, with a minimum efficiencyof 60.7% in U. rotundata. Net phosphate uptake rate wassignificantly affected by the water flow, being greatest at the highest rateassayed (2 volumes d−1). The marked decrease in tissue P shownby the three species during a flow-through experiment suggested that growth wasP limited. However, due to the increase in biomass, total P biomass increasedinthe cultures. A significant correlation was found between growth rates and thenet P biomass gained in the cultures. A three-stage design under low water flow(0.5 volumes d−1) showed that the highest growth rates (up to0.14 d−1) and integrated phosphate uptake rates(up to 5.8 μmol PO43− g−1dry wt d−1) were found in E.intestinalis in the first stage, with decreasing rates in thefollowing ones. As a result, phosphate become limiting and low increments oreven losses of total P biomass in these stages were found suggesting thatphosphate was excreted from the algae. The results show the potential abilityofthe three species to reduce substantially, at low water flow, the phosphateconcentration in waste waters from a D. labrax cultivationtank, and thus the quality of effluents from intensive aquaculture practices.

Estuarine Coastal and Shelf Science, 2005

Marine Biology, 1996

The red algaGelidium sesquipedale (Clem.) Born. et Thur. has been cultured in chemostats to asses... more The red algaGelidium sesquipedale (Clem.) Born. et Thur. has been cultured in chemostats to assess the effects of light quality and photon-fluence rate (PFR) on growth, photosynthesis and biochemical composition. Plants under blue and red light (BL and RL) showed higher growth rates than under white light (WL) of the same PFR (40 μmol m−2 s−1). The light-saturated rate of photosynthesis was higher for algae grown under BL and RL than for algae grown under WL. When algae were transferred to WL of moderate PFR (100 μmol m−2 s−1), the light-saturated rate of photosynthesis decreased, being higher in previously RL-grown algae than in previously BL- and WL-grown algae. The initial slope of photosynthesis-irradiance (PI) curves (α) was affected by PFR but not by light quality. Pigment content was little affected by light quality. Light-quality treatments also affected the biochemical composition of the alga; previous exposure to various light treatments activate or repress several metabolical pathways that are fully expressed in the subsequent phase of WL of moderate PFR. Thus, phycobiliproteins and soluble proteins increased for previously BL- and RL-grown algae, whereas insoluble carbohydrate concentration was reduced, indicating a change of the C-partitioning between carbon compounds and organic nitrogen compounds. Inorganic nitrogen metabolism was also affected by light: under WL of moderate PFR, NO3− was totally depleted from sea water, and maximal values of NO3− uptake were recorded. In addition, neither NO2− nor NH4+ was released. However, when algae were transferred to a low PFR, there was a drastic reduction of NO3− uptake under WL, which only partially recovered over time. It was accompanied by the release of NO2−, but not NH4+, to the culture medium. Under BL and RL, however, there was a transient enhancement of NO3− uptake that was followed by a net release of NO2− and NH4−. Growth rates were not correlated with PFR. This could be due to the the dynamics of internal carbon mobilization and accumulation in the algae. When algae were exposed to a moderate PFR of WL, carbon requirements for growth were satisfied by photosynthesis. Thus, there was a net accumulation of carbon in the tissue. In contrast, when algae were exposed to low PFRs of either WL, BL or RL, observed growth rates could not be maintained by photosynthesis and carbon was mobilized.

Journal of Experimental Marine Biology and Ecology, 2002

Journal of Applied Phycology, 2002

Three estuarine macroalgae (Ulva rotundata,Enteromorpha intestinalis, Gracilariagracilis) of econ... more Three estuarine macroalgae (Ulva rotundata,Enteromorpha intestinalis, Gracilariagracilis) of economic potential were cultivated in the laboratory toassess their biofiltering capacities for ammonium in waste effluents from a seabass (Dicentrarchus labrax) cultivation tank. The studywasdeveloped to investigate the functioning of N nutrition of the three species.Atlow water flow (< 2 volumes d−1) the three species strippedefficiently the ammonium dissolved in the waste water from the fish tank, withaminimum biofiltering efficiency estimate of 61% in unstarved cultures ofG. gracilis at a water flow of 2 volumesd−1. Maximum velocity for ammonium uptake (89.0 μmolNH4+ g−1 dry wth−1) was found in U. rotundata,whereas G. gracilis showed the highest affinity for thisnutrient. The net ammonium uptake rate was significantly affected by the waterflow, being greatest at the highest flow assayed (2 volumesd−1). Variations of tissue N and C:N ratios during aflow-through experiment suggested that N was not limiting macroalgal growth.However, when ammonium was supplied at a flow rate of 0.5 volumesd−1, specially in a three-stage design, the marked reductionintissue N and the biomass C:N:P ratios suggested a more general nutrientdeficiency. A significant correlation was found between growth rates and the Nbiomass gained in the cultures. The three-stage design under low water flow(0.5volumes d−1) showed that the highest ammonium uptake rates (upto 80.9 μmol NH4+ g−1 dry wtd−1 in U. rotundata) were found inthe first stage, with decreasing rates in the following ones. As a result, lowincrements or even losses of total N biomass in these stages were found,suggesting that ammonium was excreted from the algae. We conclude that thesespecies present a potential ability to biofilter the ammonium dissolved inwastewater from a D. labrax cultivation tank, suggesting thatscaling up the biofiltration designs, future practises using these macroalgaemay be implemented in the local fish farms, resulting in both environmental andeconomical advantages.

Journal of Applied Phycology, 2002

The potential of three estuarine macroalgae (Ulvarotundata, Enteromorpa intestinalis andGracilari... more The potential of three estuarine macroalgae (Ulvarotundata, Enteromorpa intestinalis andGracilaria gracilis) as biofilters for phosphate ineffluents of a sea bass (Dicentrarchus labrax) cultivationtank was studied. These seaweeds thrive in Cádiz Bay and were alsoselected because of their economic potential, so that environmental andeconomicadvantages may be achieved by future integrated aquaculture practices in thelocal fish farms. The study was designed to investigate the functioning of Pnutrition of the selected species. Maximum velocity of phosphate uptake (2.86μmol PO4 g−1 dry wth−1) was found in U. rotundata.This species also showed the highest affinity for this nutrient. At low flowrates (< 2 volumes d−1), the three species efficientlyfiltered the phosphate dissolved in the waste water, with a minimum efficiencyof 60.7% in U. rotundata. Net phosphate uptake rate wassignificantly affected by the water flow, being greatest at the highest rateassayed (2 volumes d−1). The marked decrease in tissue P shownby the three species during a flow-through experiment suggested that growth wasP limited. However, due to the increase in biomass, total P biomass increasedinthe cultures. A significant correlation was found between growth rates and thenet P biomass gained in the cultures. A three-stage design under low water flow(0.5 volumes d−1) showed that the highest growth rates (up to0.14 d−1) and integrated phosphate uptake rates(up to 5.8 μmol PO43− g−1dry wt d−1) were found in E.intestinalis in the first stage, with decreasing rates in thefollowing ones. As a result, phosphate become limiting and low increments oreven losses of total P biomass in these stages were found suggesting thatphosphate was excreted from the algae. The results show the potential abilityofthe three species to reduce substantially, at low water flow, the phosphateconcentration in waste waters from a D. labrax cultivationtank, and thus the quality of effluents from intensive aquaculture practices.

Aquaculture, 1995

... The increase in lipid deposition in muscle and liver, as well as the decrease in liver glycog... more ... The increase in lipid deposition in muscle and liver, as well as the decrease in liver glycogen, have been reported as signs of P deficiency in fish (Sakamoto and Yone, 1978). ... Food Chem., 32: 5967. Sakamoto, S. and Yone, Y., 1978. ...

Aquaculture, 1994

Pink dentex (D. gibbosus) can be considered as a potential candidate to diversify the culture of ... more Pink dentex (D. gibbosus) can be considered as a potential candidate to diversify the culture of Sparidae, due both to the importance of dentex fisheries and market within Europe, and to its phylogenetic closeness to the gilthead sea bream (Sparus aurata, Linnaeus, 1758). First trials to obtain D. gibbosus spawnings under captive conditions were carried out at the Planta Experimental de Cultivos Marinos (Instituto Canario de Ciencias Marinas, Gran Canaria, Canary Islands, Spain) in May, 1991. Broodstock management conditions determining egg quality, embryonic and larval development of D. gibbosus up to day 31 are described for the first time. Larval allometric characteristics were studied. The equation y=2.321×e0.03975x represents larval growth under experimental conditions. A comparison of egg size, hatching time and size of newly hatched larvae in several Sparidae under culture conditions is also presented. Results on broodstock acclimation, natural spawnings and larval growth rates suggest that pink dentex has a high potential for commercial culture.

Fish Physiology and Biochemistry, 2001

The aim of the present study was to determine the combined effect of both stress and EFA deficien... more The aim of the present study was to determine the combined effect of both stress and EFA deficiency on several biological and biochemical parameters. Fish were fed during 15 weeks two isocaloric and isoproteic diets: a control diet based on fish oil and formulated to meet the n-3 HUFA requirements for this species (1.5% of n-3 HUFA) and a deficient diet containing beef tallow and formulated to be deficient in n-3 HUFA. Each experimental diet was evaluated both at high and low stocking densities (10 and 3.2 kg m−3 of initial density, respectively). High stocking density produced a chronic stress situation with elevation of plasma cortisol levels. It also caused a reduction in hepatosomatic index and liver lipid contents, increasing the oleic acid/n-3 HUFA ratios in the polar lipids. Fish fed the EFA deficient diet at low stocking density showed common deficiency symptoms. High stocking density in fish fed the EFA deficient diet induced a higher degree of EFA deficiency symptoms leading to mortality, liver steatosis, liver lipid deposition, reduced muscle lipid and reduced n-3 HUFA contents, which particularly affected EPA, but not DHA, suggesting a preferential retention of the latter fatty acid, specially in the phosphoglycerides fraction.

Fish Physiology and Biochemistry, 1999

High stocking density has been shown to produce a wide variety of effects on cultured fish popula... more High stocking density has been shown to produce a wide variety of effects on cultured fish populations, such as alterations in behavior and poor feed utilization, resulting in mortality and poor growth. High stocking density has also been reported to produce chronic stress and mobilization of energy sources in fish. There are few studies focusing on the effect of high stocking density on one of the most important marine fish species for Mediterranean aquaculture, gilthead seabream (Sparus aurata). Consequently, this study investigates the effect of high stocking density on juveniles of this species, focusing on effects of stocking density on growth, biochemical composition, immune status and hematology. The results of this study showed that high stocking density produced a chronic stress situation. Plasma cortisol levels increased up to 16.25 ng ml−1 in fish held at high stocking; this value was 4 fold that of fish held at low stocking; density (3.91 ng ml−1 ). As a consequenceof this stressful situation, there was both haemoconcentration and a decrease in alternative complement pathway (ACP), an important component of the immune system of fish (from 167.23 U ml−1 down to 146.37 U ml−1). Haematocrit, haemoglobin concentration and red blood cell count were significantly higher in fish held at high stocking density (43.87%, 10.76 9dl−1 and 3.36 ×106 mm−3, respectively) compared with those fish held at low stocking density (37.21%, 9.32 g/dlg−1 and 2.82 ×106 mm−3, respectively). In addition, high stocking density produced a decrease in hepatosomatic index (from 2.26 down to 2.04) and altered liver fatty acid composition. Oleic acid (18: 1n-9) decreased in liver total lipids of fish held at high stocking density and arachidonic acid (20: 4-n6) and n-3 high unsaturated fatty acids (n-3 HUFA) were reduced in liver polar lipids of those fish. These alterations reflect the effect of stocking density on lipid metabolism to help meet the increased energy demand.

Aquaculture, 1999

High stocking density is an aquaculture-related situation which causes crowding stress in fish an... more High stocking density is an aquaculture-related situation which causes crowding stress in fish and potentially affecting the immune system. Protection against disease can be induced through immunostimulation, enhancing defence mechanisms. Vitamins C and E are among the most important nutrients influencing the immune system, although the effect of these vitamins in the amelioration of stress in fish has not been studied in detail. An experiment was carried out to study the effect dietary supplementation of vitamin C or vitamin E on the immune system of fish under a crowding stress situation in a commercial farm. A commercial diet for this species was supplemented with vitamin C or vitamin E and these diets were assayed at high stocking density (over 40 kg m−3) and the results were compared with those from fish fed the commercial diet and held at farm conditions (20 kg m−3). Some biological and immunological parameters were studied at the end of the experimental period. Fish held at high stocking density showed lower final weight than fish held at lower stocking density. These also showed higher plasma cortisol levels (over 6 ng cortisol ml−1 plasma for all the diets assayed) than those fish held at lower density (1.13 ng cortisol ml−1 plasma). High stocking density produced higher serum lysozyme activity values in fish fed the commercial diet compared with those fish held at lower density (67.49 and 36.84 units ml−1, respectively). This effect was not observed in fish held at high stocking density but fed vitamin C and vitamin E supplemented diets (lysozyme activity: 21.97 and 19.71 units ml−1, respectively). High stocking density also appeared to decrease serum alternative complement activity. In those fish fed the vitamin E supplemented diet, levels were similar to fish held at low stocking density, suggesting the role of this vitamin in this defense mechanism.

Ecological Modelling, 2003