Abstract
Detritus is a frequent, poorly defined, component of bivalve growth and carrying capacity models. The purpose of this study was to determine the proportional contributions of detrital material derived from primary producers (phytoplankton, macroalgae, Spartina alterniflora, and terrestrial leaf litter) to particulate organic matter (POM) and blue mussel’s (Mytilus edulis) diet within a temperate bay (Saco Bay, ME, United States). We assessed which detrital sources, if any, warranted incorporation into modeling efforts. Stable isotopes (δ13C and δ15N) and fatty acid biomarkers (FA) of mussels, size fractionated (<100 μm) POM, and primary producer endmembers (phytoplankton, Saccharina latissima, Ascophyllum nodosum, Chondrus crispus, Spartina alterniflora and leaf litter) collected between 2016 and 2017 were used to estimate endmember contributions to POM and mussel diets. Based on FAs dinoflagellates were the most abundant phytoplankton in Saco Bay, even during the fall diatom bloom. Diatoms within the bay were primarily centric, but pennate diatoms were at times present in the water column (e.g., in September). Following abundances of dinoflagellates, and centric and pennate diatoms, 22:6ω3 (DHA) was the most abundant essential FA (8.6 ± 0.1% total FAs), followed by 20:5ω3 (EPA: 7.0 ± 0.1%) and 20:4ω6 (ARA: 0.3 ± 0.1%). On average, phytoplankton derived organic matter contributed 22.1 ± 0.3% of the total POM in the bay. The concentration of non-fresh phytoplankton organic matter, or remaining organic matter (REMORG), was positively correlated with all endmember biomarkers. However, the proportion (%) of vascular plant, macroalgal, and detrital FAs was negatively correlated with the concentration of REMORG. This finding suggests in periods of low productivity, vascular plant and macroalgal detritus are proportionally more important contributors to POM. Mussels were broad spectrum omnivores, consuming phytoplankton, zooplankton, and detrital material. Detrital contributions to mussel diets were important (minimum of 16% of diet). Although small, macroalgae’s dietary contribution (8%) to M. edulis may be important. Macroalgal detritus contained essential FAs (20:5ω3 and 20:4ω6) that could supplement mussel diets, as M. edulis in Saco Bay were likely limited by 20:5ω3. Consideration of how macroalgal detritus affects the availability of essential FAs in POM may be useful to incorporate into aquaculture site selection.
Highlights
Bivalves, such as the blue mussel (Mytilus edulis), are an ecologically and economically important group of filter-feeding animals whose growth (Grant, 1996; Hawkins et al, 2002, 2013) and ecological carrying capacity (Byron et al, 2011a,b; Kluger et al, 2016; Outeiro et al, 2018) have been modeled based on food availability and other environmental variables
The magnitude of the discrepancy caused by the assumptions of a homogeneous detrital pool of organic matter may be small enough relative to other sources of variability to not cause a major problem in bivalve growth models
The phytoplankton community of Saco Bay was dominated by dinoflagellates, followed by centric and pennate diatoms, which directly affected the availability of essential fatty acid (FA)
Summary
Bivalves, such as the blue mussel (Mytilus edulis), are an ecologically and economically important group of filter-feeding animals whose growth (Grant, 1996; Hawkins et al, 2002, 2013) and ecological carrying capacity (Byron et al, 2011a,b; Kluger et al, 2016; Outeiro et al, 2018) have been modeled based on food availability and other environmental variables. The physical and biochemical composition of different detrital particulates determines their rate of degradation and residence time in ecosystems (Cebrian and Lartigue, 2004) as well as their bioavailability for bivalve consumers (Grant and Cranford, 1991; Duggins and Eckman, 1997; Arambalza et al, 2010; Dethier et al, 2014). Not incorporating this complexity into models may cause under or overestimations of detrital importance. By assuming all detrital material is valuable for a bivalve consumer we risk overestimating or underestimating the available food resources
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
