Zooplankton Production Research Articles

Dispersed Oil Disrupts Microbial Pathways in Pelagic Food Webs

Most of the studies of microbial processes in response to the Deepwater Horizon oil spill focused on the deep water plume, and not on the surface communities. The effects of the crude oil and the application of dispersants on the coastal microbial food web in the northern Gulf of Mexico have not been well characterized even though these regions support much of the fisheries production in the Gulf. A mesocosm experiment was carried out to determine how the microbial community off the coast of Alabama may have responded to the influx of surface oil and dispersants. While the addition of glucose or oil alone resulted in an increase in the biomass of ciliates, suggesting transfer of carbon to higher trophic levels was likely; a different effect was seen in the presence of dispersant. The addition of dispersant or dispersed oil resulted in an increase in the biomass of heterotrophic prokaryotes, but a significant inhibition of ciliates, suggesting a reduction in grazing and decrease in transfer of carbon to higher trophic levels. Similar patterns were observed in two separate experiments with different starting nutrient regimes and microbial communities suggesting that the addition of dispersant and dispersed oil to the northern Gulf of Mexico waters in 2010 may have reduced the flow of carbon to higher trophic levels, leading to a decrease in the production of zooplankton and fish on the Alabama shelf.

Mass Flux Calculations Show Strong Allochthonous Support of Freshwater Zooplankton Production Is Unlikely

Many studies have concluded terrestrial carbon inputs contribute 20–70% of the carbon supporting zooplankton and fish production in lakes. Conversely, it is also known that terrestrial carbon inputs are of very low nutritional quality and phytoplankton are strongly preferentially utilized by zooplankton. Because of its low quality, substantial terrestrial support of zooplankton production in lakes is only conceivable when terrigenous organic matter inputs are much larger than algal production. We conducted a quantitative analysis of terrestrial carbon mass influx and algal primary production estimates for oligo/mesotrophic lakes (i.e., TP≤20 µg L−1). In keeping with the principle of mass conservation, only the flux of terrestrial carbon retained within lakes can be utilized by zooplankton. Our field data compilation showed the median (inter-quartile range) terrestrial particulate organic carbon (t-POC), available dissolved organic carbon (t-DOC) inputs, and in-lake bacterial and algal production were 11 (8–17), 34 (11–78), 74 (37–165), and 253 (115–546) mg C m−2 d−1, respectively. Despite the widespread view that terrestrial inputs dominate the carbon flux of many lakes, our analysis indicates algal production is a factor 4–7 greater than the available flux of allochthonous basal resources in low productivity lakes. Lakes with high loading of t-DOC also have high hydraulic flushing rates. Because t-DOC is processed, i.e., mineralized or lost to the sediments, in lakes at ≈0.1% d−1, in systems with the highest t-DOC inputs (i.e., 1000 mg m−2 d−1) a median of 98% of the t-DOC flux is advected and therefore is not available to support zooplankton production. Further, advection is the primary fate of t-DOC in lakes with hydraulic retention times <3 years. When taking into account the availability and quality of terrestrial and autochthonous fluxes, this analysis indicates ≈95–99% of aquatic herbivore production is supported by in-lake primary production.

Responses of Zooplankton Populations to Four Decades of Climate Warming in Lakes of Southwestern Alaska

Zooplankton support a variety of important ecosystem processes in lakes but our understanding of how these organisms respond to ongoing climate change is superficial. Aquatic ecosystems have been exposed to substantial climate warming in the last century, and this trend is certain to continue, especially in northern latitudes. We analyzed a long time series of a variety of physical attributes of Lake Aleknagik, southwest Alaska, to quantify warming trends between 1963 and 2009, and to assess zooplankton community responses to variation in thermal conditions. Our analyses demonstrate clear trends toward earlier spring ice break-up, increases in average epilimnetic temperatures and an 18.5% increase in summer epilimnetic degree days since 1963. We estimated the magnitude and direction of changes in zooplankton production and end of season densities in response to changes in thermal environment, then explored whether the climate-driven responses in production are common in five large lakes that are distributed across a coastal-interior landscape gradient. Although we detected no clear directional changes in zooplankton densities or production rates, there were clear correlations between these variables and interannual variation in thermal conditions. The positive effects of earlier spring ice break-up and increase in summer degree days were strongest on the production and density responses of Daphnia and Bosmina, and the lagged effect of temperature was important and negative only for calanoid copepods. There was a negative effect of sockeye escapement to Lake Aleknagik in the previous year on all taxa. There were lake-specific effects of changes in the thermal environment on almost all taxa and small gradients in the magnitude of responses across the landscape, but no systematic patterns of landscape control.

Comparing seasonal dynamics of the Lake Huron zooplankton community between 1983–1984 and 2007 and revisiting the impact of Bythotrephes planktivory

Zooplankton community composition can be influenced by lake productivity as well as planktivory by fish or invertebrates. Previous analyses based on long-term Lake Huron zooplankton data from August reported a shift in community composition between the 1980s and 2000s: proportional biomass of calanoid copepods increased while that of cyclopoid copepods and herbivorous cladocerans decreased. Herein, we used seasonally collected data from Lake Huron in 1983–1984 and 2007 and reported similar shifts in proportional biomass. We also used a series of generalized additive models to explore differences in seasonal abundance by species and found that all three cyclopoid copepod species (Diacyclops thomasi, Mesocylops edax, Tropocyclops prasinus mexicanus) exhibited higher abundance in 1983–1984 than in 2007. Surprisingly, only one (Epischura lacustris) of seven calanoid species exhibited higher abundance in 2007. The results for cladocerans were also mixed with Bosmina spp. exhibiting higher abundance in 1983–1984, while Daphnia galeata mendotae reached a higher level of abundance in 2007. We used a subset of the 2007 data to estimate not only the vertical distribution of Bythotrephes longimanus and their prey, but also the consumption by Bythotrephes in the top 20m of water. This epilimnetic layer was dominated by copepod copepodites and nauplii, and consumption either exceeded (Hammond Bay site) or equaled 65% (Detour site) of epilimnetic zooplankton production. The lack of spatial overlap between Bythotrephes and herbivorous cladocerans and cyclopoid copepod prey casts doubt on the hypothesis that Bythotrephes planktivory was the primary driver underlying the community composition changes in the 2000s.

Secondary production of Chironomidae in a large eutrophic lake: implications for lake sturgeon production

Abstract. Most foodweb research in lentic systems has focused on pelagic primary (phytoplankton) and secondary (zooplankton) production as the primary energy sources for higher trophic-level production. Recent research has demonstrated that secondary production of benthic primary consumers can affect pelagic fish production and foodweb structure in lakes. We used the instantaneous growth method to calculate secondary production of chironomids in Lake Winnebago, Wisconsin (USA), where previous research has shown that lake sturgeon (Acipenser fulvescens) rely heavily on the benthos (chironomids) as a food source. We also used literature-derived data and the instantaneous growth method to calculate annual production of lake sturgeon to test whether chironomid production is sufficient to support the current lake sturgeon population in Lake Winnebago. We collected benthic samples with an Ekman grab at 4 profundal sites during ice-free conditions on 11 dates from spring 2008 through spring 2009. We measured in...

Review of climate change impacts on marine fish and shellfish around the UK and Ireland

ABSTRACT Recent and projected future changes in the temperature and chemistry of marine waters around the UK and Ireland are having, and will in the future have, effects on the phenology, productivity and distribution of marine fish and shellfish. However, the overall consequences are still hard to predict because behaviour, genetic adaptation, habitat dependency and the impacts of fishing on species, result in complex species' responses that may be only partially explained by simple climate envelope predictions. There is a broad body of evidence that climatic fluctuations are playing an important role in changing fish distributions and abundances, which is discernible against the background of trends in abundance due to fishing. During warm periods, southern species have tended to become more prominent and northern species less abundant. However, the changes in distribution are often more complicated than might be expected from a simple climate envelope approach, partly due to ocean circulation patterns which create invasion routes for southern water species into the North Sea from the south and from the north via the continental shelf west of Britain and Ireland. The eventual population‐scale impacts of ocean acidification on fish and shellfish are currently very difficult to predict. However, the scant evidence suggests that indirect food web effects arising from the enhanced sensitivity of calcifying planktonic organisms may be important, and the direct effect on fish sensory systems leading to subtle influences on behaviour with possible population‐level implications are possible. In British waters, the lesser sandeel (Ammodytes marinus) is identified as being at particular risk from climate change. Owing to its strict association with coarse sandy sediments it is unable to adapt its distribution to compensate for warming sea temperatures. Sandeels are a key link in the food web, linking primary and zooplankton production to top predators. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Estimation of zooplankton secondary production in estuarine waters: Comparison between the enzymatic (chitobiase) method and mathematical models using crustaceans

Sampling was seasonally performed in the Patos Lagoon estuary (Rio Grande, RS, Southern Brazil) to estimate zooplankton biomass and production comparing values obtained using an enzymatic (chitobiase) method and the traditional mathematical models based on growth. Comparison of data obtained from zooplankton samples collected with 90 and 200-μm mesh nets showed that net selectivity influences the estimation of zooplankton biomass and production. Furthermore, it showed differential results for dominance of taxa and proportions of developmental stages in samples. Differences among samples collected at the different sites in the same season were observed using either the mathematical models or the enzymatic method. The two different approaches were also able to detect the seasonal variation in production. In a broad view, data obtained using the chitobiase method showed a similar pattern of zooplankton production compared to those obtained with the traditional mathematical models based on growth. However, values estimated using the enzymatic method were systematically higher than those obtained with the mathematical models. Maximum total production values were estimated as 12.5, 9.2 and 7.9mgCm−3day−1 for the “chitobiase method”, “Huntley model”, and “Hirst model”, respectively. Considering all sampling sites and seasons, the magnitude of this difference corresponded to 1.95 and 2.49mgCm−3day−1 for the “Huntley model” and the “Hirst model”, respectively. These findings indicate the reliability of the enzymatic method in estimating crustacean production also in estuarine environments of changing salinity, as previously demonstrated for marine waters. In addition, the use of this method is more practical and comparatively less time-consuming and cheaper than the use of the mathematical models based on growth.

Survival, growth and reproduction of Daphnia galeata feeding on single and mixed Pseudomonas and Rhodomonas diets

Summary1. Bacteria can be an important resource for zooplankton production in aquatic food webs, although the degree to which bacteria sustain zooplankton growth and reproduction is not clear. We performed a growth experiment with Daphnia galeata feeding on different ratios of P‐replete Pseudomonas and Rhodomonas, ranging from a 100% bacterial to a 100% algal diet.2. A pure bacterial diet did not support survival, growth or reproduction of D. galeata. While a 20% share of Rhodomonas in the food allowed survival of daphniids, the occurrence of offspring on a 50% algal diet indicated that the threshold for successful reproduction was between those two proportions of algal food. Increasing the proportion of the alga further increased growth and reproductive output, indicating that Rhodomonas was a higher‐quality food than Pseudomonas.3. A subsequent labelling experiment demonstrated that D. galeata incorporated phosphorus from Pseudomonas and Rhodomonas with similar efficiency, whereas carbon was incorporated more efficiently from Pseudomonas than from Rhodomonas.4. we hypothesise that inadequate levels of essential biochemicals in pure bacterial diets led to decreased Daphnia performance. Concentrations of fatty acids in general, and especially of polyunsaturated fatty acids, were much lower in Pseudomonas than in Rhodomonas. This difference could explain the different growth and reproduction responses, although limitation by other essential biochemicals (e.g. sterols) cannot be ruled out.5. Hence, where they dominate, bacteria may provide a significant part of the elemental flux to species feeding higher in the food web on the short term. However, the performance of consumers may be constrained by essential biochemicals.

Variation of chitobiase-based estimates of crustacean zooplankton production rates in high latitude waters

Community-level estimates of mesozooplankton productivity are required for calculating the magnitude and efficiency of energy flow through planktonic food webs. However, estimates of biomass production rates (BP) for entire crustacean zooplankton communities are lacking, because conventional field methodology is difficult to apply at the community level. We measured community-level BP using the chitobiase method in an area extending from the west coast of British Columbia, Canada, across the Bering and Chukchi Seas and into the western Beaufort Sea (July 2008, October 2008, and July 2009). Our objective was to measure zooplankton productivity on a scale that was sufficiently broad to allow us to assess the sensitivity of the method to a wide variety of conditions. Overall, variations in temperature and phytoplankton biomass explained 67% of the observed variation in BP. Crustacean zooplankton BP values estimated during July 2008 and 2009 on the Bering Sea shelf were comparable to estimates from one of the very few community-level estimates for this expansive region. Our estimates of the average individual growth rate (daily P/B) for crustacean zooplankton were also comparable to model predictions and direct estimates for the biomass-dominant copepod species in the northern Gulf of Alaska. These observations suggest that the chitobiase method can be used to measure useful estimates of community-level crustacean zooplankton productivity under a broad range of conditions and also provides the basis for further refinement of the technique.

MODELING NUTRIENT (DISSOLVED INORGANIC NITROGEN) AND PLANKTON DYNAMICS AT SAGAR ISLAND OF HOOGHLY–MATLA ESTUARINE SYSTEM, WEST BENGAL, INDIA

Abstract Degradation of litter from mangrove forests adjacent to the creeks at Sagar Island of the Hooghly–Matla estuarine ecosystem is one of the principal sources of nutrient to the estuary. Nutrients augment the growth of phytoplankton, which in turn stimulates the production of zooplankton. Zooplankton serves as major food source for fish population of this estuarine system. Here, a dynamic model with three state variables (nutrient, phytoplankton, and zooplankton) is proposed using nitrogen (mgN/l) as currency. Input of dissolved inorganic nitrogen as nutrient, water temperature, surface solar irradiance, and salinity of upstream and downstream of the estuary, collected from the field, are incorporated as graph time functions in the model. Calibration and validation are performed by using collected data of two consecutive years. Model results indicate that the growth of zooplankton and phytoplankton are enhanced by increase in nutrient input in the system. Zooplankton biomass is affected by decrease in the salinity of the estuary. Sensitivity analysis results at ±10% indicate that maximum growth rate of phytoplankton (Pmax) is the most sensitive parameter to the nutrient pool although growth rate of zooplankton (gz) and half saturation constant for phytoplankton grazing by zooplankton (Kz) are most sensitive parameters to phytoplankton and zooplankton compartments, respectively. The model depicts the present status of plankton dynamics, which serve as major food resource for herbivorous and carnivorous fish species of the estuary. Effect of deforestation is tested in the model. Therefore, from management perspective, this model can be used to predict the impact of mangroves on nutrient and plankton dynamics, which will give complete information of both shell and fin fish productions in the estuary.

Subsidy or Subtraction: How Do Terrestrial Inputs Influence Consumer Production in Lakes?

Cross-ecosystem fluxes are ubiquitous in food webs and are generally thought of as subsidies to consumer populations. Yet external or allochthonous inputs may in fact have complex and habitat-specific effects on recipient ecosystems. In lakes, terrestrial inputs of organic carbon contribute to basal resource availability, but can also reduce resource availability via shading effects on phytoplankton and periphyton. Terrestrial inputs might therefore either subsidise or subtract from consumer production. We developed and parameterised a simple model to explore this idea. The model estimates basal resource supply and consumer production given lake-level characteristics including total phosphorus (TP) and dissolved organic carbon (DOC) concentration, and consumer-level characteristics including resource preferences and growth efficiencies. Terrestrial inputs diminished primary production and total basal resource supply at the whole-lake level, except in ultra-oligotrophic systems. However, this system-level generalisation masked complex habitat-specific effects. In the pelagic zone, dissolved and particulate terrestrial carbon inputs were available to zooplankton via several food web pathways. Consequently, zooplankton production usually increased with terrestrial inputs, even as total whole-lake resource availability decreased. In contrast, in the benthic zone the dominant, dissolved portion of the terrestrial carbon load had predominantly negative effects on resource availability via shading of periphyton. Consequently, terrestrial inputs always decreased zoobenthic production except under extreme and unrealistic parameterisations of the model. Appreciating the complex and habitat-specific effects of allochthonous inputs may be essential for resolving the effects of cross-habitat fluxes on consumers in lakes and other food webs.

Abundance dynamics and functional role of predaceous Leptodora kindtii in the Curonian Lagoon

Abstract The abundance and distribution of predatory cladoceran Leptodora kindtii was investigated in the estuarine lagoon (Curonian Lagoon, SE Baltic Sea). Three hydrodynamically different parts of the lagoon were selected, representing transitory oligohaline, intermediate freshwater and stagnant freshwater sites. L. kindtii was least abundant at the oligohaline site, never occurring at salinities greater than 4 psu. At the two freshwater sites, the abundance of L. kindtii varied from a low of &lt;0.1 up to 2.2 indv. L−1 during peak abundance. Two peaks of L. kindtii abundance were observed with timing differences between stations: at the stagnant site the population of L. kindtii peaked two weeks earlier relative to the more hydrodynamically active sites, likely due to a 2°C higher May temperature. The small body size of L. kindtii in the lagoon (seasonal mean 2.68±0.6 mm) shows high fish predation pressure and predicts small cladocerans, juvenile copepods and rotifers being in the preferred prey size range. The calculated L. kindtii daily consumption during the population peak was as high as 100% of the daily zooplankton production, which implies high potential of this predator to shape the grazing zooplankton community in the lagoon.

Changing climate increases biological productivity in the Arctic

Climate change is leading to increased biological productivity in the coastal Arctic. As ice melts and recedes far from land, winds interact with open waters to increase the upwelling of nutrient‐rich deep water and stimulate biological productivity. Tremblay et al. quantified these changes using remote sensing and in situ observations in the coastal Beaufort Sea. They found that ice ablation and the combination of increased upwelling and greater light penetration into the water column during fall 2007 and summer 2008 increased the production of ice algae, phytoplankton, and zooplankton by 2–6 times. (Geophysical Research Letters, doi:10.1029/2011GL048825, 2011)

Biomass and estimated production properties of size-fractionated zooplankton in the Yellow Sea, China

The size-fractionated zooplankton biomass, taxonomic composition, and production calculated by formulas basing on Ikeda–Motoda's physiological methods were studied on the basis of samples taken from six cruises in the Yellow Sea. Zooplankton was size-fractionated using sieves into ~2mm, 1–2mm, 0.5–1mm, 0.25–0.5mm and 0.16–0.25mm groups. The results showed that the average zooplankton biomass was 84.03mg DM m−3 in May, followed in order by September, June, March, August and December with 42.34, 38.36, 32.37, 27.17 and 21.83mg DM m−3, respectively. The contribution of ~2mm, 1–2mm, 0.5–1mm, 0.25–0.5mm and 0.16–0.25mm groups to the total biomass was in the range of 15.2–27.4%, 13.2–29.4%, 14.7–18.2%, 15.8–22.6% and 16.3–34.2%, respectively, during the investigating period. The biomass of all size groups was all highest in May, and except that the biomass of 0.16–0.25mm group was lowest in August, the biomass of other size groups was lowest in December. The dominant zooplankton species (or taxa) in each group were similar between six cruises. The estimated zooplankton production was highest in May with 1.97mg C m−3d−1, and was lowest in December with 0.51mg C m−3d−1, and was in the range of 0.67–1.44mg C m−3d−1 in other investigating months. The estimated annual zooplankton production was 0.37g C m−3y−1. The two smallest groups aggregately comprised 59–84% of the net-zooplankton production in the Yellow Sea. The geographical distribution of size-fractionated zooplankton biomass and production was significantly affected by the complex physical features of the Yellow Sea. When the Yellow Sea Cold Bottom Water appeared from June to September, the biomass and production of zooplankton larger than 1mm were higher inside the cold water mass area than outside it, while the zooplankton smaller than 1mm showed contrary results. The higher biomass and production of all zooplankton groups occurred in the southern part of the study area in December due to the intrusion of the Yellow Sea Warm Current. And in March, the higher zooplankton biomass and production, especially for small size zooplankton, occurred at the coastal waters resulting from complex physical properties. Results of the present paper showed the biomass and production properties of size-fractionated zooplankton, which is very important for “parameterization” of food web structure models of the Yellow Sea.

Zooplankton productivity at the peak of eutrophication of a plain reservoir ecosystem: The role of invertebrate predators

Changes in metazooplankton productivity and the pressure of invertebrate predators in the Rybinsk Reservoir are analyzed on materials of long-term studies (1956–1995). The production of the plankton community was shown to be twice as high (72.5 kcal/m2) in 1990–1995 as in 1950–1970, i.e., typical for aquatic ecosystems of the eutrophic type. About 70% of the production (33.7 kcal/m2 of nonpredatory cladocerans; 7.3, rotifers; 3.9, nonpredatory copepods; 3.2, predatory cladocerans; and 1.4, omnivorous and predatory cyclopoid copepods) was available to meet the food demands of fish. In summer (June–July), strained trophic relations were registered between predatory and nonpredatory zooplankters. A strong effect of Mesocyclops and Thermocyclops on the abundance and structure of the community was revealed: for a season they consumed 11.6 kcal/m2 of the metazooplankton production, and the index of their total impact was 0.21–0.22. The limitation of the number and productivity of the small fraction of metazooplankton (especially of rotifers) by invertebrate predators is discussed.

‘State of Lake Superior’: A review

‘State of Lake Superior’: A review

Climate forcing multiplies biological productivity in the coastal Arctic Ocean

[1] The effects of changing ice and atmospheric conditions on the upwelling of deep nutrient-laden waters and biological productivity in the coastal Beaufort Sea were quantified using a unique combination of in situ and remote-sensing approaches. Repeated instances of ice ablation and upwelling during fall 2007 and summer 2008 multiplied the production of ice algae, phytoplankton, zooplankton and benthos by 2 to 6 fold. Strong wind forcing failed to induce upward shifts in the biological productivity of stratified waters off the shelf.

Density-Dependent Growth in Juvenile Sockeye Salmon (OncorhynchusNerka)

Data gathered over 77 lake-years from 4 coastal British Columbia sockeye salmon nursery lakes suggest that density-dependent growth reductions are only possible at exceptionally high fry densities. In Great Central Lake (n=33 years) and Sproat Lakes (n=30 years) there was no relationship between smolt weight and mean summer fry densities ranging from 760-3800 fry ha -1 . However, in two years when Sproat Lake fry densities were unusually high (1983=5183 ha -1 , 1996=4801 ha -1 ) smolt weights were among the lowest recorded. In Woss and Vernon lakes (n=14 lake-years), there were significant bottom-up relationships between fall-fry weights and zooplankton biomass, but no relationships between December-fry weights and average fry densities (range 331-1361 ha -1 ), nor were there significant top-down relationships between fry densities and average zooplankton biomass. Comparisons of zooplankton production with bioenergetic-based fry consumption, suggested that the carrying capacity for Vernon Lake which had the highest rate of zooplankton production, was 12,700 fry ha -1 , and for Sproat Lake which had the lowest zooplankton production, was 5200 fry ha -1 . We conclude that fry densities in the range commonly observed for British Columbia coastal lakes (i.e. 500-4000 ha -1 ) cannot cause density-dependent reductions in prey biomass or fry growth rates. Further research is necessary.

Defining the optimal dose of chicken droppings for specific production of zooplankton for aquaculture

In order to determine the optimal dose of chicken droppings to be used for the massive production of zooplankton in a controlled environment, the productions of various species of zooplankton in fertilized tanks with four doses of chicken droppings were tested (D150 = 150 g/m3; D300 = 300 g/m3; D600 = 600 g/m3 and D1200 = 1,200 g/m3). Comparisons were made between the doses as well as with a non-fertiliser control (D0 = 0 g/m3). The experimentation was carried out in triplicate in 12 fertilized tanks and 3 control tanks, each filled with 500 litres of water. Five days after fertilization, the zooplankton was stocked in the tanks at a density of 15 ind/L, i.e. initial biomass of 11.36 μg/L. The physico-chemical and biological parameters of the culture were followed throughout the 45-day period of experimentation. Results show that primary production is high with rates D300, D600, D1200. The best biomass of phytoplankton expressed by measuring chlorophyll-a was obtained with dose D1200 (p < 0.05). The optimal conditions to combine the development of the phytoplankton and its consumption by the zooplankton were however obtained with doses D300 and D600. In terms of zooplankton production, increasing doses of manure resulted in increasing yields of zooplankton. Hence, the highest productions of zooplankton were obtained with doses D300, D600 and D1200 where the dry biomasses were respectively 866 ± 235 μg/L, 905 ± 179 μg/L and 492 ± 132 μg/L, i.e. fresh biomasses estimated about 8,6 mg/L, 8,7 mg/L and 4,7 mg/L. With dose D1200, the abundance of phytoplankton negatively influenced the production of zooplankton. In practice, doses 300 g/m3 and 600 g/m3 are recommended as the optimum rate of chicken droppings to be used for the massive production of zooplankton within the conditions of this experiment.

Production and prey source of juvenile black rockfish Sebastes cheni in a seagrass and macroalgal bed in the Seto Inland Sea, Japan: estimation of the economic value of a nursery

The economic value of ecosystem services of vegetated habitats (seagrass and macroalgal beds) has been estimated to be among the highest of the various ecosystems on earth. However, fish production has not been included in the evaluations due to the difficulty of quantitative estimation of fish production in the field. In the present study, annual production and economic value of wild juvenile black rockfish, Sebastes cheni, a dominant fish species in seagrass and macroalgal beds in the central Seto Inland Sea were estimated. Juvenile S. cheni migrated into vegetated habitats at about 20 mm total length (TL) and grew up to about 60 mm TL by late May. Juvenile abundance was highest in April (2007) or March (2008). Eight cohorts with the same extrusion period (each cohort covering a 10-day period) were identified using otolith daily increments. The annual estimates of S. cheni juvenile production were 13,080 g ha−1 year−1 in 2007 and 18,360 g −1 year−1 in 2008. Based on the unit price of artificially raised S. cheni juveniles, the economic value of the annual wild juvenile production was converted to 654,000 JPY (Japanese yen: 100 JPY = ca. 1 USD) ha−1 year−1 for 2007 and 918,000 JPY ha−1 year−1 for 2008. Analyses of stomach contents and stable isotope (δ13C or δ15N) showed that juvenile S. cheni were highly dependent on copepods. The planktonic trophic pathway originating from phytoplankton supports the majority of the juvenile black rockfish production during the post-migration period (20–60 mm TL) in the seagrass and macroalgal beds through the production of copepod zooplankton. The total economic value of the ecosystem services of the vegetated habitat is suggested to be much higher than estimates in previous studies if the provisioning and regulating services which originate from fish production were included in the estimates.