Seasonality in coastal macrobenthic biomass and its implications for estimating secondary production using empirical models

Abstract

Macrobenthic secondary production is widely used to assess the trophic capacity, health, and functioning of marine and freshwater ecosystems. Annual production estimates are often calculated using empirical models and based on data collected during a single period of the year. Yet, many ecosystems show seasonal variations. Although ignoring seasonality may lead to biased and inaccurate estimates of annual secondary production, it has never been tested at the community level. Using time series of macrobenthic data collected seasonally at three temperate marine coastal soft-bottom sites, we assessed seasonal variations in biomass of macrobenthic invertebrates at both population and community levels. We then investigated how these seasonal variations affect the accuracy of annual benthic production when assessed using an empirical model and data from a single sampling event. Significant and consistent seasonal variations in biomass at the three study sites were highlighted. Macrobenthic biomass was significantly lower in late winter and higher in summer/early fall for 18 of the 30 populations analyzed and for all three communities studied. Seasonality led to inaccurate and often biased estimates of annual secondary production at the community level when based on data from a single sampling event. Bias varied by site and sampling period, but reached $ 50% if biomass was sampled at its annual minimum or maximum. Since monthly sampling is rarely possible, we suggest that ecologists account for uncertainty in annual production estimates caused by seasonality.

Secondary production increases with species richness but decreases with species evenness of benthic invertebrates

“…An implicit assumption of our analysis is therefore that the ‘snapshots' of taxon biomass used to estimate production are representative of annual values. This is unlikely to be wholly accurate, and by using data from summer, when population densities and body mass tend to peak, we are likely to have overestimated annual production to some extent (Saulnier et al 2019). Nevertheless, an overestimation of annual production throughout the study area is unlikely to reduce the ability of our analysis to detect relationships between biodiversity and production, particularly as our models incorporate explanatory variables that capture seasonal change (i.e.…”

Dynamic Changes of the Mu Us Sandy Land and Relevant Causes

“…This was also beneficial for use in the semi-elastic model, as described below. The specific explanation for these log values is as follows [25][26][27][28][29].…”

Food limitation of juvenile marine fish in a coastal and estuarine nursery

“…where CR is a seasonal ratio (unitless) that converts macrobenthic biomass into mean annual biomass (estimated from Saulnier et al 2019; Supplement S3), is the total biomass observed during the survey (g AFDM), is the production-to-biomass ratio (yr -1 ) estimated using an empirical model (Brey 2012), is a regeneration coefficient (unitless) that represents somatic regeneration after sublethal predator cropping (Tableau et al 2015) and is the energy density (kJ.g AFDM -1…”

“…In temperate ecosystems, juvenile marine fish concentrate in nursery grounds from late spring to early fall, when the biomass of macrobenthic prey peaks (Beukema 1974;Saulnier et al 2019).…”