|What is the effect of seasonality on macrobenthic population dynamics in a marine site of the Westerschelde Estuary?|
Brackenborough, N. (2021). What is the effect of seasonality on macrobenthic population dynamics in a marine site of the Westerschelde Estuary?. BA Thesis. NIOZ Royal Netherlands Institute for Sea Research: Yerseke.
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Temperature is one of the major seasonally fluctuating factors influencing estuarine ecosystems. Only a handful of studies have investigated the seasonal progressions of estuarine macrobenthic communities, and even fewer have researched the macrobenthos of the Westerschelde Estuary. Two replicate sediment cores were sampled bimonthly from Paulina Polder, a mud-flat in the marine region of the Westerschelde Estuary. The analysis conducted on the sampled macrobenthos produced several measures of population dynamics, including headcount and biomass measurements per m2, as well as Shannon diversity and richness calculations. The purpose of this research was to determine the seasonal changes in these data and to relate the observed trends to previous studies. Headcounts were found to be highest in the cooler months, as were diversity and richness. Biomass followed a similar trend except in November, where biomass was low relative to headcount. This was attributed to the presence of smaller animals or juveniles that month. The four most abundant taxa – Heteromastus filiformis, Alitta succinea, Oligochaeta and Cyathura carinata – demonstrated varying growth and breeding periods. All four population dynamic indices were lowest in July, argued to be due to the relative absence of the sediment ventilator H filiformis, to the June 2019 heat wave and/or to the amplifying effect of increasing temperatures on bivalve predation. O2 consumption (respiration rate) by the macrobenthos was found to be most correlated with biomass, increasing as biomass increased. Temperature and microbial life are suggested to be additional influences of the observed O2 trends. This research concludes that (1) seasonal changes in temperature, (2) seasonal differences in breeding and growth patterns of the taxa and (3) seasonal difference in predation, effect the population dynamics of estuarine benthos.