Modeling food web interactions in benthic deep-sea ecosystems: a practical guide

Deep-sea benthic systems are notoriously difficult to sample. Even more than for other benthic systems, manyflows among biological groups cannot be directly measured, and data sets remain incomplete and uncertain. In such cases, mathematical models are often used to quantify unmeasured biological interactions. Here, we show how to use so-called linear inverse models (LIMs) to reconstruct material and energy flows through food webs in which the number of measurements is a fraction of the total number of flows. These models add mass balance, physiological and behavioral constraints, and diet information to the scarce measurements. We explain how these information sources can be included in LIMs, and how the resulting models can be subsequently solved. This method is demonstrated by two examples—a very simple three-compartment food web model, and a simplified benthic carbon food web for Porcupine Abyssal Plain. We conclude by elaborating on recent developments and prospects

One foot in the grave: zooplankton drift into the Westerschelde estuary (The Netherlands)

The net growth rate of marine zooplankton entering the Westerschelde estuary was investigated using an advective-dispersive transport model that simulates zooplankton biomass behaving conservatively in the estuary. Total biomass of marine zooplankters in the Westerschelde was much lower than what would be expected based on transport alone, indicating negative growth rates in the estuary. Including a net consumption term in the transport model allowed the estimation of total net mortality. About 3% of all marine zooplankters that enter the Westerschelde with the flood currents are retained in the estuary, where they die. On average, 5% of the total marine zooplankton biomass in the estuary died per day. Each year a net amount of about 1500 t of zooplankton dry weight (DW) is imported from the sea to the estuary. Thus in the Westerschelde the marine zooplankton persists mainly due to continuous replenishment from the sea. Average net production/biomass rates of the major marine zooplankton species varied from -0.02 g DW (gDW)-1 d-1 (Temora longicornis) to -0.39 g DW (gDW)-1 d-1 (Pseudocalanus elongatus). In the estuary, the differential mortality of these species resulted in shifts in dominance within the zooplankton community relative to that in the sea. Possible causes of this zooplankton mortality are discussed

Estimating secondary production for the brackish Westerschelde copepod population <i>Eurystemora affinis</i> (Poppe) combining experimental data and field observations

Eurytemora affinis (Poppe) (Copepoda : Calanoida) development is studied through cultures supplied with naturally occurring particulate matter (Western Schelde estuary) and kept at six constant temperatures in the range 2-20-degrees-C. At 2-degrees-C the copepods do not reach the copepodite stages and at 5-degrees-C, do not develop further than the fourth copepodite stage. A field production estimate is given combining the biomass present in the field and weight specific growth rates derived from the culture experiment. The P/B obtained are very close with those measured for the same species in other estuaries

Leven in troebel water: het planktonische leven in het estuariene water

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MOSES: model of the Scheldt estuary: ecosystem model development under SENECA

The ecosystem model was developed for the Westerschelde, and aims to provide a mathematical description of the Scheldt estuary ecosystem, to determine the origin and fate of organic carbon in the estuary, its role in the foodweb, and especially the relative importance of phytoplankton primary produciton, and to test the possibilities of SENECA as a model development too

Present nitrogen and carbon dynamics in the Scheldt estuary using a novel 1-D model

A 1-D, pelagic, reactive-transport model of a completely mixed, turbid, heterotrophic estuary – the Scheldt estuary – is presented. The model resolves major carbon and nitrogen species and oxygen, as well as pH. The model features two organic matter degradation pathways, oxic mineralisation and denitrification, and includes primary production as well as nitrification. Apart from advective-dispersive transport along the length axis, the model also describes O&lt;sub&gt;2&lt;/sub&gt;, CO&lt;sub&gt;2&lt;/sub&gt;, and N&lt;sub&gt;2&lt;/sub&gt; air-water exchange. The aim of this study is to present a model which is as simple as possible but still fits the data well enough to determine the fate and turnover of nutrients entering the estuary and their spatial patterns in the years 2000 to 2004. Nitrification is identified as one of the most important processes in the estuary, consuming a comparable amount of oxygen as oxic mineralisation (1.7 Gmol O&lt;sub&gt;2&lt;/sub&gt; y&lt;sup&gt;&amp;minus;1&lt;/sup&gt; vs. 2.7 Gmol O&lt;sub&gt;2&lt;/sub&gt; y&lt;sup&gt;&amp;minus;1&lt;/sup&gt;). About 10% of the 2.5 Gmol of nitrogen entering the estuary per year is lost within the estuary due to denitrification. Nitrogen and carbon budgets are compared to budgets from the seventies and eighties, showing that nitrification activity has peaked in the eighties, while denitrification steadily declined. Our model estimates an average CO&lt;sub&gt;2&lt;/sub&gt; emission of 3.3 Gmol y&lt;sup&gt;&amp;minus;1&lt;/sup&gt; in the years 2001 to 2004, which is a comparatively low estimate in the context of previous estimates of CO&lt;sub&gt;2&lt;/sub&gt; export from the Scheldt estuary