Effects of the suspension feeding musselMytilus trossuluson a brackish water macroalgal and associated invertebrate community (original) (raw)
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Marine Ecology, 2009
The importance of suspension-feeding mussels is particularly apparent in benthic communities; however, the role of this feeding strategy on the development of macroalgal and associated invertebrate communities is in general poorly known. The effect of suspension-feeding mussels Mytilus trossulus on benthic communities was studied in an in situ factorial field experiment in the Northern Baltic Sea over one ice-free season. The experiment was performed under different regimes of wave exposure (low and moderate) and on different sedimentary habitats (soft bottom with high organic content, soft bottom with low organic content, and hard bottom). In general the presence of mussels was associated with increased biomass of filamentous algae, herbivores and deposit feeders and decreased biomass of charophytes. The effect of M. trossulus interacted with the effect of exposure and substrate. Stronger responses were observed in moderately exposed than in sheltered areas. The presence of M. trossulus affected charophytes and deposit feeders on sand with low content of organic matter and filamentous algae on pebbles but not on other substrate types. The magnitude of the effects varied between months. The results suggest that (i) even in dynamic coastal systems the biodeposits and excretions of mussels are at least partly assimilated locally and are not flushed away to the open sea, (ii) the accumulation of faecal material induced elevated growth of deposit feeders, (iii) mussels enhanced the growth of ephemeral macroalgae and reduced the growth of perennial macroalgae, and (iv) together with increasing benthic primary production, mussels indirectly increase the production of herbivores.
Nutrient regeneration by mussel Mytilus edulis spat assemblages in a macrotidal system
Journal of Sea Research, 2014
Besides exercising grazing control over phytoplankton populations, suspension-feeding bivalves can also stimulate carrying capacity by regeneration of nutrients. This study provides new data on nutrient uptake and release dynamics, and potential implications for availability and stoichiometry of nutrients, for Mytilus edulis spat collectors in the Netherlands. Uptake and release rates were measured in situ on intact spat collector ropes in a eutrophic macrotidal system in relation to development of ropes in terms of mussel biomass and associated components (fauna, flora, organic material). There was a good fit between uptake/release rates and mussel weight based on allometric scaling functions, despite the occurrence of a substantial biomass of associated fauna, flora and organic matter on ropes. On a unit biomass basis, nutrient release rates were much higher than reported in other studies, which we attribute to greater activity of small mussels. Accounting for greater weightspecific activity of small mussels, spat collectors released more P than reported for other systems. We show that spat collectors can affect relative availabilities of N, P and Si, and we show that SMCs likely stimulated phytoplankton production through regeneration of N and of Si, which were at limiting concentrations at different points in time. In the case of Si, stimulation would be restricted to diatoms. We conclude that SMCs are able to stimulate phytoplankton production rates, and thereby carrying capacity, and are able to influence phytoplankton composition.
Diet of mussels Mytilus trossulus and Dreissena polymorpha in a brackish nontidal environment
Marine Ecology, 2013
Benthic suspension feeders have traditionally been considered an important link between pelagic and benthic food webs in shallow seas. Their ecological impact depends highly on the removal rate of pelagic production from the water column. Besides phytoplankton, benthic suspension feeders can feed on microphytobenthos and detritus suspended in the water column by wind-waves or tidal forces. The share of the pelagic component in the diet of benthic suspension feeders is poorly studied in the non-tidal environment. We examined the diatom food items of two bivalve species, Mytilus trossulus Gould and Dreissena polymorpha Pallas, at four shallow locations in the Gulf of Riga basin, in the Baltic Sea, differing in hydrographic characteristics. The share of pennate benthic diatoms was always higher in mussel food than in ambient water, whereas pelagic species were under-represented. Mussels never consumed the dominant genera that were in the water column, Cylindrotheca and Leptocylindrus. There were no differences in the main food source between the two mussel species. Our results suggest that the impact of benthic suspension feeders on pelagic foodwebs and their role in promoting benthic-pelagic coupling is of a minor importance in the study area, whereas the impact on benthic food webs may be mainly by the rearrangement of energy within benthic pathways.
Diet of mussels Mytilus trossulus and Dreissena polymorpha in a brackish nontidal environment
Marine Ecology, 2013
Benthic suspension feeders have traditionally been considered an important link between pelagic and benthic food webs in shallow seas. Their ecological impact depends highly on the removal rate of pelagic production from the water column. Besides phytoplankton, benthic suspension feeders can feed on microphytobenthos and detritus suspended in the water column by wind-waves or tidal forces. The share of the pelagic component in the diet of benthic suspension feeders is poorly studied in the non-tidal environment. We examined the diatom food items of two bivalve species, Mytilus trossulus Gould and Dreissena polymorpha Pallas, at four shallow locations in the Gulf of Riga basin, in the Baltic Sea, differing in hydrographic characteristics. The share of pennate benthic diatoms was always higher in mussel food than in ambient water, whereas pelagic species were under-represented. Mussels never consumed the dominant genera that were in the water column, Cylindrotheca and Leptocylindrus. There were no differences in the main food source between the two mussel species. Our results suggest that the impact of benthic suspension feeders on pelagic foodwebs and their role in promoting benthic-pelagic coupling is of a minor importance in the study area, whereas the impact on benthic food webs may be mainly by the rearrangement of energy within benthic pathways.
Goods and Services of Marine Bivalves
Cultured and wild bivalve stocks provide ecosystem services through regulation of nutrient dynamics; both by regeneration of nutrients that become available again for phytoplankton production (positive feedback), and by extraction of nutrients through filtration and storage in tissue (negative feedback). Consequently, bivalves may fulfil a role in water quality management. The magnitude of regulating services by filter feeding bivalves varies between coastal ecosystems. This review uses the blue mussel as a model species and evaluates how cultured mussel stocks regulate nutrient dynamics in oligo-meso-and eutrophic ecosystems. We thereby examine (i) the eco-physiological response of mussels, and (ii) the positive and negative feedback mechanisms between mussel stocks and the surrounding ecosystem. Mussel culture in nutrient-poor areas (deep Norwegian fjords) are compared with cultures in other coastal systems with medium-to rich nutrient conditions. It was found that despite differences in eco-physiological rates under nutrient-poor
Marine Biology, 2006
Using radiotracer (14 C) and microscopic observation, we demonstrated that mussels (Mytilus edulis and Perna viridis) could be predators of mesozooplankton (rotifer Brachionus plicatilis). At radio-labelled rotifer densities of 0.1, 0.2, 0.5, 1.0 individual ml À1 , faecal pellets of mussels showed different degrees of radio signals and most of the faecal pellets were expelled 4 h after pulse feeding on rotifers. The maximum gut retention time (GRT) of 14 C-labelled rotifers in the digestive diverticula did not o show any significant difference between the two mussel species or the different densities of rotifers, and the averaged GRT was 43.4±3.06 h (mean ± SE). At a rotifer density of 4.5 individual ml À1 , rotifer lorica pieces and rotifer bodies without eggs were found in faeces of M. edulis, while in the pseudofaeces, only complete rotifer bodies were found.
Journal of Experimental Marine Biology and Ecology, 2008
The Grande-Entrée Lagoon (Magdalen Islands, Canada) has supported mussel (Mytilus edulis) cultivation for the last 25 years. Algal biomass in this lagoon is relatively low while heterotrophic plankton biomass is high. Although often considered herbivorous, it is known that filter-feeding bivalves can consume various types of food, from bacteria to zooplankton. We hypothesize that along with phytoplankton, heterotrophs constitute an important food resource for the Grande-Entrée mussels. In situ mesocosm experiments were undertaken at different seasons using short socks filled with mussels from the same cohort taken from an aquaculture farm, in order to determine the impact of cultured mussels on local plankton communities and assess the role of heterotrophs. Filtration activity by the mussels and associated epibionts present in the socks was expressed as clearance rates (CR). The average CR over all taxa was lowest in June and highest in October. Diatoms, dinoflagellates and heterotrophic protists constituted the bulk of planktonic carbon removed by mussels. While smaller-sized taxa contributed little (b 5%) to mussel carbon intake, large-sized heterotrophs (namely ciliates) contributed 69 to 88%. Taxon-marker pigment analyses generally confirmed these observations for groups containing phototrophic pigments. The high heterotrophic biomass retained by mussels indicates they are a major food source for mussels in this environment and should be considered both in the evaluation of mussel feeding and in assessing the influence of cultured mussels on local plankton ecosystems.
2010 International Conference on Biosciences, 2010
Benthic suspension feeders are very important in coupling and energy transfer between benthos and plankton. Hence, it becomes essential to know which factors regulate the feeding activity of suspension feeders. In an in situ experiment seasonal variability in the biodeposition of Mytilus trossulus was related to temperature, salinity, current velocity, total chlorophyll a (Chl a equivalent), and the biomass of phytoplankton species in the northern Baltic Sea. The biodeposition was explained by current velocity interacting with ambient Chl a and temperature. The biodeposition increased curvilinearly with ambient concentration of Chl a eq suggesting that the saturation reduction occurred above 10 μg Chl a eq l -1 . The biomass of benthic diatoms (Pennales) better described the biodeposition of M. trossulus than the other studied variables. The result suggests that a significant part of its diet consists of benthic microalgae. The population of M. trossulus could remove on an average less than 3% of phytoplankton stock daily and, hence, had a minor effect on phytoplankton populations in the study area.
Hydrobiologia, 2005
Fluxes of oxygen, nitrogen and phosphorus were determined in two areas of the Sacca di Goro lagoon, at a site influenced by the farming of the mussel Mytilus galloprovincialis and a control site. Mussel farming induced intense biodeposition of organic matter to the underlying sediments, which stimulated sediment oxygen demand, and inorganic nitrogen and phosphorus regeneration rates compared to the nearby control station. Overall benthic fluxes (-11.4 ± 6.5 mmol O 2 m)2 h)1 ; 1.59 ± 0.47 mmol NH 4 + m)2 h)1 and 94 ± 42 lmol PO 4 3) m)2 h)1) at the mussel farm are amongst the highest ever recorded for an aquaculture impacted area and question the belief that farming of filter-feeding bivalves has inherently lower impacts than finfish farming. In situ incubations of intact mussel ropes demonstrated that the mussel rope community was an enormous sink for oxygen and particulate organic matter, and an equally large source of dissolved inorganic nitrogen and phosphate to the water column. Overall, a one meter square area of mussel farm (mussel ropes and underlying sediment) was estimated to have an oxygen demand of 46.8 mmol m 2 h)1 and to regenerate inorganic nitrogen and phosphorus at rates of 8.5 and 0.3 mmol m 2 h)1 , with the mussel ropes accounting for between 70 and more than 90% of the overall oxygen and nutrient fluxes. Even taking into account that within the farmed area of the Sacca di Goro lagoon, there are 15-20 m)2 of open water for each one covered with mussel ropes, the mussel ropes would account for a large and often dominant part of overall oxygen and nutrient fluxes. These results demonstrate that it is essential to take into account the activity of the cultivated organisms and their epiphytic community when assessing the impacts of shellfish farming. Overall, whilst grazing by the mussel rope community could act as a top-down control on the phytoplankton, most of the ingested organic matter is rapidly recycled to the water column as inorganic nutrients, which would be expected to stimulate phytoplankton growth. Consequently, the net effect of the mussel farming on phytoplankton dynamics, may be to increase phytoplankton turnover and overall production, rather than to limit phytoplankton biomass.