Model of copepod growth influenced by the food carbon:nitrogen ratio and concentration, under the hypothesis of strict homeostasis (original) (raw)
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Is the growth of marine copepods limited by food quantity or quality?
Limnology and oceanography letters, 2021
Marine copepods are ubiquitous and play important roles in sustaining fish stocks, nutrient cycling, and carbon sequestration in deep waters. Our ability to represent these tiny animals in ocean biogeochemical models is hindered by an incomplete understanding of how the quantity and quality of food influence their growth. Using a state-of-the-art model that includes an explicit representation of metabolism, and which has carbon and nitrogen as currencies, we demonstrate that copepod growth is limited by the quantity of organic matter consumed when feeding on typical marine phytoplankton. Our work highlights the benefit of incorporating realistic physiology into plankton models and paves the way for improved predictions of the role of copepods in models of fish production and global biogeochemical cycles.
Effect of food quality on carbon and nitrogen growth efficiency in the copepod Acartia tonsa
Marine Ecology Progress Series, 2002
Populations of the copepod Acartia tonsa were fed a mixture of algal prey (diatom Thalassiosira weissflogii, prymnesiophyte Emiliania huxleyi, dinoflagellate Aureodinium [Gymnodium] pigmentosum) supplied at saturating concentrations, grown under either nitrogen-sufficient or nitrogen-deplete conditions, in order to study the impact of food quality on production and development throughout the life cycle of the copepod. Changes in predator population structure and biomass were recorded, along with consumption of each of the algal groups, permitting C and N growth efficiencies to be estimated. There was a clear difference in the Acartia tonsa population structure when fed N-sufficient or N-deplete prey, with those fed N-deplete prey slower to develop and reproduce and laying fewer eggs. Algal nutrient status affected selectivity between the diatom and dinoflagellate, the latter being favoured under nutrient-deplete conditions, perhaps in part because their C:N ratio was less susceptible to altered nutrient status. There was no clear difference in the N growth efficiency (N-GE, typically 5%) between N-sufficient and N-deplete prey, but certainly efficiency did not increase with N-deplete prey. C growth efficiency (C-GE) declined from 5 to 2% with N-deplete prey. However, while the ratio of N-GE:C-GE was clearly different between N-sufficient (1) and N-deplete (2.5) treatments, actual growth efficiencies increased with time during the progression to later life history stages, culminating in highest efficiencies during active egg production. Caution should be exercised in assigning GE and predation rates in models incorporating zooplankton feeding on prey of variable nutrient status; these parameters are not constants and GE estimates from egg production experiments are likely to significantly overestimate efficiencies over the whole copepod life cycle.
Marine Ecology Progress Series, 1987
The chemlcal composihon was analyzed of faecal pellets produced by copepods from Bedford Basin (Nova Scotia, Canada), mainly Pseudocalanus spp. and Temora longicornis, fed dfferent concentrations of the diatom Thalassiosira weissflogii. The feeding response of copepods to day-to-day changes in food concentration involved adjustments of ingestion rate in < 24 h; die1 differences in ingestion rate were found In copepods acclimated to high food concentration but not in those acclimated to low food concentration. Carbon and nitrogen content of faecal pellets (percentage of dry weight) was independent of food concentration, acclimation period to a given food concentration, and ingestion rates. Mean pellet composition was 25 % C and 3 % N; a higher C:N ratio in faecal pellets (7 to 9) as compared with that of the food (5.5) suggested that N was assimilated more efficiently than C. These results suggest that single values of the chemical composition of pellets might be used to estimate vertical flux of carbon and nitrogen via zooplankton faecal pellets. However, a comparison with literature data suggests that differences in carbon and nitrogen content of copepod faecal pellets might result from differences in food quality.
Plankton and Benthos Research
The freshwater calanoid copepod Mongolodiaptomus malaindosinensis is an endemic species of the lower Mekong basin, including Malaysia. The relationships between environmental factors and life history traits have been reported for many copepods, while they have never been assessed in this tropical species. Post-embryonic development time (post-EDT), body size and survival rate of M. malaindosinensis were determined under different algal concentrations of Chlamydomonas reinhardtii and Cryptomonas tetrapyrenoidosa at 25°C, to clarify the effects of algal species and carbon supply on their somatic growth and survival. Post-EDT until adult in M. malaindosinensis decreased with increasing food carbon supply regardless of the algal species tested. Although naupliar developments were the shortest at 10 4 cells mL −1 of C. reinhardtii, food shortage delayed the development time and also induced high mortality during the copepodid stages. The highest survival rate of 93% was obtained in the copepods fed on C. tetrapyrenoidosa at 5 10 4 cells mL −1 , whereas the survival rates in the remaining lower carbon supply were <23%. The most sensitive stages were the 1st copepodid stage, as indicated by high stage-specific mortalities, because of large morphological and physiological changes in this transitional stage. Prosome length of adult M. malaindosinensis positively correlated with food carbon supplies, though females were larger than males. Somatic growth rate exponentially increased with increasing food carbon supplies with a threshold at around 4.0 mgC L −1. These results suggest that tropical copepods may be adapted to higher food quantities due to their high metabolic rates under high temperature conditions.
Bioenergetics of the copepod Temora longicornis under different nutrient regimes
Journal of Plankton Research
The copepod Temora longicornis depends on constant prey availability, but its performance also depends on how efficiently it utilizes its food sources. Our research goal was to understand copepod energy allocation in relation to diet quality. The working hypothesis was that Temora performs better on the diet whose elemental ratio is closest to its own. Diatoms (Diat) and dinoflagellates (Dino) cultured in nutrient-replete (+) and nitrogen-depleted (−) conditions were fed to the copepods. Ingestion, respiration, excretion and egg and fecal pellet production rates were measured. Carbon (C) and nitrogen (N) budgets were built to investigate differences in dietary C and N partitioning. Copepods fed nitrogen-depleted diatoms (Diat−), which had the most different C:N ratio to that of Temora longicornis, had high metabolic losses and low growth. Copepods fed nitrogen-rich dinoflagellates (Dino+) with a more similar C:N ratio to their own also had high metabolic losses, but displayed the highest investment into somatic growth and egg production. The results indicate that dinoflagellates are a better food source for T. longicornis. Furthermore, consumption of low-quality food leads to higher respiration rates and faster leakage of dissolved organic carbon from copepod fecal pellets; and egestion is a main pathway in copepods for eliminating unabsorbed and non-metabolized carbon.
Effects of food quality on the functional ingestion response of the copepod Acartia tonsa
Marine Ecology Progress Series, 1987
Effects of food quality on the functional ingestion response of the copepod Acartia tonsa were determined using 3 algal species 6 to 12 pm in diameter (dinoflagellate Amphidnium carten, coccol~thophorid Hymenomonas carterae, senescent and actively growing diatom Thalass~osira weissflogii), over a wide range of concentrations. The algal cells were characterized by their contents of carbon, nitrogen, prote~n, carbohydrate, lipid and chlorophyll a, and by dry weight. A. tonsa Ingestion rates Increased to an asymptote and were fit to the Ivlev model without a feeding threshold at low algal concentratlons. Maximum ingestion rates of algal cells were inversely proportional to their protein, nitrogen, and carbon content. Maximum lngeshon rates of protein and nitrogen increased w t h increasing cell content of these variables. In contrast, maximum ingestion rates of algal carbon were generally constant w t h increasing cellular carbon content. The effects of cellular carbohydrate, hpid, and chlorophyll a content on maximum ingeshon rates were variable. The rate at which the ingestion of phytoplankton cells approached the maximum ingestion rate increased w t h greater protein and nitrogen content. Our results suggest that cellular protein and nitrogen content (or factors related to them) are important in regulating A. tonsa ingestion rates.
The effects of food stoichiometry and temperature on copepods are mediated by ontogeny
Oecologia, 2018
Climate change is warming the oceans, increasing carbon dioxide partial pressure and reducing nutrient recycling from deep layers. This will affect carbon (C) and phosphorus (P) availability in the oceans, thus, altering the balance between the nutrient content of consumers and their food resource. The combined effects of food quality and temperature have been investigated for adult copepods; however, nauplii, the early developmental stages of copepods, often far outnumber adults, grow more rapidly and have a higher phosphorus body content and demand than later life stages. Consequently, ontogeny may affect how copepods respond to the combined stressors of increasing temperature and altered food stoichiometry. We conducted temperature-controlled experiments (24, 28 and 32 °C) where Parvocalanus crassirostris was fed either a P-replete or a P-limited phytoplankton food source. Reduced survival of nauplii and copepodites at the highest temperature was ameliorated when fed P-replete fo...
Examining the Effects of Different Diets and Salinities on Copepod Population Growth
2016
The coastal oceans are subject to climate impacts leading to sea level rise, increases in the frequency and intensity of storms, and increased precipitation. These events can lead to a rise in the amount of fresh water entering coastal ecosystems from runoff or rainfall, which cause decreases in ocean salinity. Understanding marine food web dynamics requires an understanding of how species interactions will respond to environmental changes of this kind. Sea urchins are key members of nearshore food webs and may help to link food availability between shallow and deep zones along coastal areas. Sea urchins posess a very inefficient digestive system, which means that their feces may possess large amounts of available nutrients which other organisms can use as a viable food source. This research studied the population growth of T. californicus copepods in both low salinity and normal seawater environments, and with diets of either fresh Ulva or urchin fecal Ulva. The calorie content for...
Journal of Experimental Marine Biology and Ecology, 2008
Nitrogen excreted as ammonium, urea, and dissolved primary amines (DPA), and nitrogen ingested by the planktonic calanoid copepod, Acartia tonsa, were measured while fed 4 foods with different N/C ratios in high (500 μg C l − 1) and low (50 μg C l − 1) concentrations. Adult copepods were fed the ciliate, Uronema marinum (N/C = 0.26), the diatom, Thalassiosira weissflogii, in log-phase growth (N/C = 0.20), and in senescent-phase growth (N/C = 0.12), and detritus derived from the saltmarsh grass, Spartina alterniflora, (N/C = 0.04). Total nitrogen excreted ranged from 0.06 to 0.18 μg N copepod − 1 d − 1 whereas nitrogen ingested exhibited considerably more variation (0.01 to 0.39 μg N copepod − 1 d − 1). Ammonium was the dominant form of nitrogen excreted and was influenced by both food concentration and N/C ratio. Copepods fed foods with N/C ratios resembling their own body composition (log-phase diatoms and ciliates) excreted more ammonium when fed higher concentrations of food. In contrast, copepods fed foods with lower N/C ratios than their own body composition excreted more ammonium when fed lower concentrations of food, suggesting that they were catabolizing body protein for survival. Excretion of urea varied with food N/C ratio, with more urea excreted when the copepods were fed higher N/C foods. The excretion of DPA did not vary with either food concentration or food N/C ratio. Homeostasis serves to conserve the N/C ratio of copepods. Thus nitrogen excretion by healthy copepods should be expected to increase with ingestion only when copepods have high quantities of nitrogen-rich foods relative to the body composition of the copepods.