Estimates Of Secondary Production Research Articles

Secondary production of benthic molluscs from the delaware bay and coastal area

Secondary production of benthic molluscs was estimated for one Delaware Bay site and two coastal Delaware sites for 1980 and 1981. Direct measurements of production ( P = mg AFDW m −2 year −1), mean biomass ( B = mg AFDW m −2 ) and turnover ratios ( P: B ) for six select species ranked as follows: Ensis directus ( P = 6·1–8674·0, B = 1·2–1230·4 , P: B = 5·0–14·1 ); Mytilus edulis ( P = 0·2–13384·2, B = 0·2–2169·5 , P: B = 1·0–6·2 ); Nucula annulata ( P = 16·7–844·0, B = 10·3–604·8 , P: B = 0·4–6·2 ; Nucula proxima ( P = 1·7-1·9, B = 0·3-0·4 , P: B = 1·8-5·7 ); Spisula solidissima ( P = 0·6–873·9, B = 0·4–194·4 , P: B = 1·5-5·7 ); and Tellina agilis ( P = 136·1–7648·0, B = 19·4–2782·4 , P: B = 2·1–7·0 ). Indirect measurements of remaining mollusc species accounted for a range of 26·2–59·0% of total mollusc production. Total mollusc production was highest at the Delaware Bay station (21775·0 mg AFDW m −2 year −1), slightly lower at the coastal station nearest the Bay mouth (19206·3 mg AFDW m −2 year −1) and markedly lower at the coastal station furthest from the Bay mouth (1571·0 mg AFDW m −2 year −1). This pattern also reflected an association with sediment type as production was higher in fine sand than in coarse sand. Peak production varied seasonally and there was considerable annual variability at two stations. It was concluded that estimates of secondary production and turnover ratios of dominant Delaware Bay area molluscs were similar to estimates for the same species or related species from other similar habitats.

Dynamics of Lake Michigan Plankton: A Model Evaluation of Nutrient Loading, Competition, and Predation

Lake Michigan's offshore ecosystem has been altered dramatically during the past decade. Summer zooplankton dominance has changed from calanoid copepods to Daphnia and the substantial contribution of filamentous blue-green algae to summer phytoplankton has been replaced by phytoflagellates. These changes occurred concurrently with reduced P load, P concentration, and abundance of the dominant zooplanktivore, the alewife (Alosa pseudoharengus). In this analysis we pose alternative hypotheses of nutrient loading and species interactions as determinants of zooplankton and phytoplankton species composition in the summer epilimnion. We evaluate these hypotheses with a food web model that was calibrated to measurements of the 1980s Lake Michigan plankton composition and algal production, sedimentation, and growth rates and literature estimates of zooplankton secondary production and nutrient excretion. The model simulates the influence of gradients of both P load and alewife abundance on predation–competition interactions. We conclude that summer plankton composition in Lake Michigan is controlled largely by predation. The model further predicts a return to a plankton community similar to that of the 1970s under a scenario of increasing invertebrate predation by a new zooplankton species for Lake Michigan, Bythotrephes cederstroemi.

Experimental test of an allometric method for estimating potential copepod production

Phytoplankton and zooplankton, collected in November 1984 at the deepest point of Bedford Basin, Canada, were used in a 2 mo experiment in the Dalhousie tower tank to test the validity of estimating potential copepod production from allometric equations based on body size and temperature under food-saturated conditions (“maximum instantaneous growth, MIG” method). The development of the plankton community in the mesocosm was similar to fall and winter assemblages in a coastal Nova Scotian inlet. Predicted instantaneous rates of potential production were compared with average production of a mixed copepod assemblage measured over weekly intervals in the absence of predators. Predictions exceeded measured production by 1.9 to 136 times, but generally agreed within an order of magnitude. Whereas the MIG method facilitates automated estimation of potential copepod production, this advantage must be offset by the relative loss of accuracy compared to more labour-intensive methods. The method appears to be most useful for mesoscale surveys or neritic regions where the aim is to quickly obtain an order of magnitude estimate of secondary production.

Optimal allocation of effort in studies using the size‐frequency method of estimating secondary production

Secondary production estimates based on the size‐frequency method can be improved through the use of optimal sample allocation without increasing the total sampling effort. We advocate a two‐step procedure. First, sampling dates should be chosen to minimize bias. Then, sample sizes on each date should be allocated in such a way as to minimize variance. Calculating the optimal sample allocation requires some prior variance information, but even rather imperfect information will usually result in improved estimates. An example is presented using published data on the mayfly Ephemerella dorothea.

The Estimation of Secondary Production of the Marine Bivalve Spisula subtruncata (DA COSTA) in the Area of the Po River Delta

Abstract. The secondary production of Spisula subtruncata (somatic production) is calculated in the framework of a benthic monitoring study in a coastal area. The temporal trends of density, biomass and growth increments are examined in the three year‐classes present. These are compared to certain physical and chemical parameters.

Macroinverfebrate Abundance and Production of Psammophifous Chironomidae in Shifting Sand Areas of a Lowland River

Abundance and biomass of benthic macroinvertebrates from shifting sand areas in the bed of the Sand River in central Alberta, Canada, were examined for 1 yr. Macroinvertebrate density ranged from 12 000 to 78 000 individuals/m2, but total biomass was low (50–490 mg/m2 dry mass) due to the small size of most organisms. The interstitial larvae of two chironomid species (Robackia demeijerei and Rheosmittia sp.) contributed a mean of 80.6% biomass and 92.8% of total number of macroinvertebrates. Total annual secondary production of these two species (752.0 ± 144.5 mg∙m−2∙yr−1) was used as an estimate of total secondary production of benthic macroinvertebrates in shifting sand areas. Both R. demeijerei and Rheosmittia sp. exhibited larval growth and development rates much slower than those reported for comparably sized species in other habitats. Food or frequent disturbance may limit the growth of these species. Although unit area biomass and production were low relative to other lotie habitats, shifting sand areas make significant contributions to the river ecosystem because they occupy a large proportion of the river bed.

Long-Term Estuarine Variability and Associated Biological Response

Corpus Christi Bay, one of seven major Texas estuaries, is characterized by low freshwater inflow, small tidal flushing, low annual rainfall, and high evaporation rates. Minimal exchange of water makes this estuary sensitive to episodic environmental variation caused by sudden surges of freshwater from flooding rains or hurricanes. It is suggested that this episodic variability stimulates estuarine production. For the last 11 years, detailed data have been collected on benthic community structure, primary and secondary productivity, and sediment nutrient regeneration which are combined with other information, such as fishery yields, into a reconstructed long-term data set. During this same period significant environmental changes in the estuary have been documented. In 1979 the lowest salinity recorded over the 11-year record was related to a short-term, high intensity rainfall. The benthos responded with abundance and biomass levels far greater than any other year during the study interval. Correlated with increased benthic production were large increases in shrimp yields. During more subtle changes with respect to freshwater input in 1981, significant alterations in primary productivity were quantified. Primary, secondary, and tertiary carbon production estimates derived from the reconstructed long-term data base indicated the benthos as a major link between primary producers and other consumers. Carbon flow from primary producers, however, appeared inadequate to support benthic production. Nutrient recycling was judged to provide more than 90% of nitrogen needed to support phytoplankton production and was considered a major factor influencing ecosystem function. The matching of biological responses to significant environmental changes in this estuary provided insight into ecosystem function and stressed the importance of short-term variability. Although recycling was identified as a major source of nutrients supporting primary production, it was concluded that episodic environmental change from freshwater input provided a much needed stimulus to productivity. These episodic changes replaced materials lost through recycling and sustained productivity over the long term.

Secondary production of four sublittoral, soft-sediment amphipod populations in the Bay of Fundy

Estimates of secondary production by cohort summation of losses and size–frequency methods were made on the four most abundant amphipods at an 80 m deep station on a soft sediment in the southwestern mouth of the Bay of Fundy. Production and annual turnover ratios (production:biomass ratio (P:B), in parentheses) for the 1978 year class, expressed as grams wet preserved weight per square metre per year, were as follows: Haploops fundiensis, 0.505 (1.3); Photis reinhardi, 0.370 (2.8); Casco bigelowi, 1.210 (2.5); Harpinia propinqua 0.066 (3.1). The P:B ratios found were closest to those calculated by the empirical method of Robertson when an accurate estimate of life-span was available.

A simulation analysis of continental shelf food webs

Energy flow through continental shelf food webs was examined using a simulation model. The model structure expands the two traditional marine food chains of phytoplankton-zooplankton-pelagic fish and benthos-demersal fish into a complex web which includes detritus, dissolved organic matter (DOM), bacteria, protozoa, and mucus net feeders. Simulation of energy flux for different shelf systems using the expanded web revealed that heterotrophic microorganisms and their predators account for a significant component of the energy flux in the continental shelf ecosystem. Contrary to previous models, where all phytoplankton were considered to be grazed by zooplankton, our simulation results indicate that only slightly more than 50% of the annual net primary production is grazed. A substantial quantity of the phytoplankton production directly becomes detritus. Bacteria mineralize detritus and DOM produced by phytoplankton and other components of the food web, converting these to biomass with high efficiency. Consequently, the model predicts that planktonic bacterial production is equivalent to zooplankton production. Exclusion of the bacteria requires the assumption that all DOM is either exported from the system or consumed by another component of the food web. Neither of these assumptions can be supported by present knowledge of the dynamics of DOM in the sea. Model simulations were also employed to test the hypothesis that production exceeds consumption on continental shelves, resulting in exports of 50% of the annual primary production. Simulations of shelves with high rates of primary production resulted in a particulate export of 27% and realistic estimates of secondary production. Results of other simulations suggest that shelves with lower primary production cannot export production and still maintain the macrobenthos and their predators. General properties about continental shelves can also be inferred from the model. From simulations of shelves of differing primary production, nanoplankton are predicted to account for a greater proportion of the primary production in nutrient limited systems. Benthic production appears to be related to both the quantity of primary production and the sinking rates of the phytoplankton. The model indicates that zooplankton fecal inputs to the shelf benthos are only a small portion of the total detrital flux, leading to the prediction that fecal pellets are of little significance in determining benthic production. Finally, the model generates production efficiencies that are highly variable depending on the type of system and kind of populations involved. We argue that the assumed ecological efficiency of 10% should be abandoned for continental shelves and other ecosystems.

The estimation of secondary production in a natural population of Daphnia hyalina (Leydig) using alternative methods of computation

A single set of population data for Daphnia hyalina was used to estimate production using four methods on a daily and annual basis. Estimates varied from 12.94 to 50.60 g dry weight m-2 y-1. The differences obtained are attributed to faults in the method such as the ignoring of post embryonic development times and poor estimates of basic variables used for the calculations. The latter include poor estimations of specific parts of the population census, particularly egg estimates, and choice of values used for weight estimates and duration times of stages. The normally used birth rate model probably underestimates production whereas the growth increment method probably overestimates production.

Review of the Biological Oceanography of the Strait of Georgia: Pelagic Environment

Different components of the food web in the Strait of Georgia are reviewed. The phytoplankton are dominated by diatoms; however, flagellates may dominate in the winter. Chlorophyll a concentrations may range from < 1 mg∙m−3 in the winter to > 15 mg∙m−3 during blooms. The average annual primary productivity is about 280 g C∙m−2 for the strait, but it is higher in frontal areas at the north and south ends of the strait and near the Fraser River plume. Light limits primary productivity during the winter months, while nutrients (nitrogen) and grazing are the limiting factors during the late spring and summer. Turbidity and salinity effects occur near the Fraser River plume. The surface macrozooplankton community is composed chiefly of copepods. Mid- and deep-water communities consist of euphausiids, chaetognaths, and some deep-living copepods, which overwinter at depth. The standing stock of macrozooplankton (> 350 μm) to 400 m, ranges from 0.1 to 2.0 g wet wt∙m−3. Few estimates of secondary production and standing stock estimates of microzooplankton have been made. Horizontal patches of zooplankton have been encountered and may be important feeding sites for some fish. Standing stock associations of the dominant species in the food web of the strait are reasonably well known, but assessment of food web dynamics from these limited standing stock measurements is often inaccurate. There is a noticeable absence of data on how rate processes affect standing stocks, and it is particularly an understanding of these interrelationships that is needed for fisheries management. There is an urgent need for more interaction between biological oceanographers and fisheries scientists, particularly in the area of zooplankton grazing by larval fish.

Production Estimates for Scotian Shelf Copepods Based on Mass Specific P/B Ratios

We estimated annual secondary production by copepod species on the Emerald Bank, Scotian Shelf, for the first time. We tentatively ranked copepod species in order of importance based on production to biomass (P/B) ratios calculated from adult body mass using an empirical relationship. The significance of assessing species in terms of production rather than population biomass is demonstrated. The mean estimate of total copepod production (530 kJ∙m−2) is in good agreement with previous estimates of secondary production on the Scotian Shelf.

Size-frequency estimates of secondary production byMysis relicta in Lakes Michigan and Huron

Data from five Great Lakes studies ofMysis relicta populations were reanalyzed to calculate secondary production estimates using the size-frequency method. Production estimates (P) ranged from 0.25 to 3.2 g dry weight m−2 yr−1. Average annual biomass {xxB} and mean annual density (xxD) were 0.11–1.11 g dry weight/ m2 and 25–434 animals/ m2, respectively. P:{xxB} ratios varied only between 2.2 and 3.3. Maximum and minimum biomass values within a study varied by a factor of 519 for one study but by less than 17 for the others. Highest estimates of P, {xxB} and {xxD} were calculated for collections from a 50-m station in Lake Michigan despite the larger populations suspected to be present at greater depths sampled in the other studies. These conservative estimates provide a basis for scaling trophic interactions involvingM. relicta and emphasize findings by previous workers that night-time sampling with vertical net hauls is the best available technique for quantitative studies ofM. relicta populations in the Great Lakes.

Methods for estimating secondary production in marine Amphipoda

For the 1971 year-class of Pontoporeia femorata from St. Margaret's Bay, N.S., secondary production was 11.06–13.61 g wet weight/m2 and annual turnover ratio was 3.64–4.78 as measured by three methods. These included cohort summation of losses, integrated production from the Allen curve, and size frequency, or modified Hynes methods. Sampling bias against early life history stages of amphipods collected with sieve meshes [Formula: see text] can be corrected by back calculation from population data thus enabling cohort-based estimates of secondary production to be made.Key words: secondary production, annual turnover ratio, Pontoporeia femorata, Crustacea, Amphipoda

Influence of Benthos Life History upon the Estimation of Secondary Production

Synchrony of cohorts is one of the life history features having most important effects upon the estimation of benthic secondary production, because most methods depend heavily upon recognition of discrete cohorts. The Hynes method, intended to circumvent the necessity of cohort distinction, still depends upon determination of trophic level, voltinism, minimum and maximum sizes, and length of aquatic life. Knowledge of preferred habitat, distribution, and behavior are essential for accurate production estimates. Use of the production:mean standing stock (P/B) ratio (fairly constant at about 5 for cohort P/B of benthic invertebrates) to approximate production from standing stock data, also must account for trophic level, voltinism, and length of aquatic life. Various life history features are compared as to their probable effect on production estimation; in addition, they are compared to the effect of sampling errors. Key words: benthos, life history, production, secondary production, productivity

Sampling Variability and Life History Features: Basic Considerations in the Design of Aquatic Insect Studies

Sampling variability in benthic studies may result from sampling device operation, physical features of the environment, laboratory sorting procedures, and biological features of study populations. Selected factors and procedures that influence variability, samplers affected, and proposed remedies are presented. Consequences of not considering autecological components in sampling designs are illustrated by analysis of larval counts of Cheumatopsyche pettiti (Banks), a multiple cohort caddisfly with an aggregated population. The range of mean numbers of C. pettiti was great with low sample numbers. Aggregation is more reliably measured at low sample numbers with the Index of Dispersion and the Mean Crowding Index than with the dispersion parameter k, the calculation of which from the maximum-likelihood equation, is integrally related to sample size. Nonrandom patterns of C. pettiti observed from samples collected in an Indiana, USA, stream riffle, may result from a failure to consider hyporheic distributions, spatial influences (e.g. sampling both favored and nonfavored microhabitats), instar-specific differences, and behavioral features. Variability in secondary production estimates of an aggregated population of Ceraclea ancylus (Vorhies) from a Kentucky, USA, stream indicated similar relationships to sample size.The size of the mean, the degree of aggregation, and the desired precision of the mean estimate will influence the number of samples required to estimate densities of benthic populations. Sample size requirements calculated from data reported in previous studies were high to achieve accepted levels of precision. Habitat stratification may reduce the numbers of samples required. Dicosmoecus gilvipes (Hagen) exhibited nonaggregated patterns and required fewer samples to estimate density in uniform substrate areas of a California, USA, river pool than did aggregated populations in both mixed substrate areas and the entire pool. Ceraclea ancylus required fewer samples for density estimates in stratified (by habitat or substrate type) than unstratified habitats, the fewest samples being necessary when the individual stone was the sampling unit. Judicious choice of study populations may permit larger numbers of samples to be collected and processed with reduced cost, as an alternative to stratification. Larvae of C. ancylus and D. gilvipes could be separated in the field; density underestimation due to a hyporheic population component was eliminated because of surface dwelling behavior or by choice of study sites; and compounded spatial distributions due to co-occurring instar-specific patterns were absent because the populations have a single cohort.Larger numbers of samples may be necessary than are generally taken in benthic studies. Further research is needed to assess variability in secondary production estimates and community diversity analyses. Improved methods for substrate surface area estimation and increased use of experimental approaches and sequential sampling techniques should be considered in future benthic sampling designs. Key words: sampling, benthos, aquatic, macroinvertebrate, Trichoptera, insect, experimental design, autecology, life history, variability

Aspects of Estimating Zooplankton Production from Phytoplankton Production

Primary productivity and zooplankton data from Ocean Station P are used to compare estimates of phytoplankton and herbivore production calculated on the assumption of continuous grazing by the animals with estimates obtained on the assumption of three different types of nocturnal grazing. Effective plant production, that corrected for the effects of grazing on the size of the phytoplankton stock and hence on the magnitude of the plant respiratory loss, was less than the measured production and was least under the assumption of continuous grazing. The small differences in effective production resulting from the choice of different grazing schemes resulted in large differences in estimates of secondary production. The relative effect of assuming different grazing schemes on the estimate of secondary production varied markedly with zooplankton respiration and with the phytoplankton growth rate.