Linking Intertidal and Subtidal Food Webs: Consumer-Mediated Transport of Intertidal Benthic Microalgal Carbon

Abstract

We examined stable carbon and nitrogen isotope ratios for a large variety of consumers in intertidal and subtidal habitats, and their potential primary food sources [i.e., microphytobenthos (MPB), phytoplankton, and Phragmites australis] in a coastal bay system, Yeoja Bay of Korea, to test the hypothesis that the transfer of intertidal MPB-derived organic carbon to the subtidal food web can be mediated by motile consumers. Compared to a narrow δ13C range (−18 to −16‰) of offshore consumers, a broad δ13C range (−18 to −12‰) of both intertidal and subtidal consumers indicated that 13C-enriched sources of organic matter are an important trophic source to coastal consumers. In the intertidal areas, δ13C of most consumers overlapped with or was 13C-enriched relative to MPB. Despite the scarcity of MPB in the subtidal, highly motile consumers in subtidal habitat had nearly identical δ13C range with many intertidal foragers (including crustaceans and fish), overlapping with the range of MPB. In contrast, δ13C values of many sedentary benthic invertebrates in the subtidal areas were similar to those of offshore consumers and more 13C-depleted than motile foragers, indicating high dependence on phytoplankton-derived carbon. The isotopic mixing model calculation confirms that the majority of motile consumers and also some of subtidal sedentary ones depend on intertidal MPB for more than a half of their tissue carbon. Finally, although further quantitative estimates are needed, these results suggest that direct foraging by motile consumers on intertidal areas, and thereby biological transport of MPB-derived organic carbon to the subtidal areas, may provide important trophic connection between intertidal production and the nearshore shallow subtidal food webs.

Natural history matters: Plastics in estuarine fish and sediments at the mouth of an urban watershed

“…This is consistent with other ontogenetic dietary shifts observed in California killifish, such as changes in prey types, prey sizes, prey abundance, and microhabitat use with time [85,86]. These fish may, in turn, be important vectors for transferring small plastics and contaminants to the broader coastal food web given their abundance, their roles in connecting intertidal with both subtidal and terrestrial ecosystems, and their roles as forage fish for many species [92][93][94][95]. While examples of the transfer of plastics between trophic levels are on the rise [30][31][32][33], needed is a better understanding of the mechanisms underlying the pathways of…”

Blue Carbon Storage Capacity of Temperate Eelgrass (Zostera marina) Meadows

“…Site‐specific values for measured plant variables are given in Table S2. Due to lack of in situ sampling of phytoplankton at the sites, δ 13 C values from the literature were used in the stable isotope analysis (Conway‐Cranos et al, ; Goering et al, ; Jorgensen et al, ; Kang et al, ; Kajihara et al, ; Miyajima et al, ; Pernet et al, ; Röhr et al, ; Tagliabue & Bopp, ; Tiselius & Fransson, ). The δ 13 C values for plankton selected from the literature for each site and used in the analysis are given in Table S3.…”

Understanding marine food web dynamics using fatty acid signatures and stable isotope ratios: Improving contaminant impacts assessments across trophic levels

“…Benthic microalgae and kelp have a higher carbon isotopic ratio than phytoplankton which could be a possible carbon source at the base of the echinoderm food chain (France, 1995). Bioturbation of refractory organic matter (poorly biodegradable leftovers of organisms) in the sediment could also cause an enrichment of δ 13 C if consumed by benthic primary consumers (Nadon and Himmelman, 2006), (Kang et al, 2015). It can be concluded that the more complex and pelagic the food web, the more degraded material reaches the sea floor.…”