Determination of Trophic Transfer at a Created Intertidal Oyster (Crassostrea ariakensis) Reef in the Yangtze River Estuary Using Stable Isotope Analyses

Abstract

Oysters can create reefs that provide habitat for associated species resulting in elevated resident abundances, lower mortality rates, and increased growth and survivorship compared to other estuarine habitats. However, there is a need to quantify trophic relationships and transfer at created oyster reefs to provide a better understanding of their potential in creating suitable nekton habitat. Stable isotope analyses (δ 13 C and δ 15 N) were conducted to examine the organic matter sources and potential energy flow pathways at a created intertidal oyster (Crassostrea ariakensis; hereinafter, oyster) reef and adjacent salt marsh in the Yangtze River estuary, China. The δ 13 C values of most reef-associated species (22 of 37) were intermediate between those of suspended particle organic matter (POM) and benthic microalgae (BMI), indicating that both POM and BMI are the major organic matter sources at the created oyster reef. The sessile and motile macrofauna colonizing the reef make up the main prey of transient nekton (e.g., spotted sea bass, Asian paddle crab, and green mud crab), thus suggesting that the associated community was most important in supporting higher trophic levels as opposed to the direct dietary subsidy of oysters. The created oyster reef consistently supported higher trophic levels than the adjacent salt marsh habitat due to the dominance of secondary consumers. These results indicate that through the provision of habitat for associated species, created oyster reefs provide suitable habitat and support a higher average trophic level than adjacent salt marsh in the Yangtze River estuary.

Oyster and Associated Benthic Macrofaunal Development on a Created Intertidal Oyster (Crassostrea Ariakensis) Reef in the Yangtze River Estuary, China

“…1A: N6, N8-N9, S5, S7-S8, S9), covering approximately 10 km of the reef at a mean density of 5.6 oysters/m 2 . The oysters at the reef were identified initially as the jinjiang oyster (Crassostrea rivularis), but were later recognized as the Asian oyster (C. ariakensis) according to the recent classification based on shell morphology and flesh color (Wang et al 2004, Quan et al 2012. Furthermore, identification of oyster species at the DNCRP reef was completed using multiplex species-specific PCR genetic markers; more than 85% of oyster specimens were recognized as C. ariakensis (others were identified as Crassostrea sikamea) (Quan, unpubl.…”

“…1B). Dense oysters and typical 3-dimensional reef structure (dead and live oyster matrix) only appeared in the lower (MLW) and middle (1.2 m MLW) intertidal zone, whereas sporadic oysters are distributed in the high (2.5 m MLW) intertidal zone of the created reef (see Quan et al 2009, Quan et al 2012). …”

“…The structurally complex surface that oysters create can provide a unique habitat for reef-associated benthic organisms that serve as prey for economically and ecologically important nekton species (Harding & Mann 2001, Luckenbach et al 2005, Quan et al 2012. A number of studies have used quantitative or qualitative methods to investigate species demographics on natural or restored oyster reefs (e.g., Dame 1979, Larsen 1985, Zimmerman et al 1989, Wenner et al 1996, Luckenbach et al 2005, Rodney & Paynter 2006, Walters & Coen 2006, Taylor & Bushek 2008, Lejart & Hily 2011.…”

“…Previous studies have demonstrated that the created oyster reef is able to support sustainable oyster (C. ariakensis) populations (Quan et al 2009), provide important ecosystem services (Quan et al 2007), create significant habitat structure for resident and transient species (Quan et al 2009), and maintain a higher average trophic level and more robust food web than adjacent saltmarsh (Quan et al 2012). This study explored the development (from reef creation to year 5) of the oyster population and associated benthic macrofaunal communities using sites along an exposure and salinity gradient on the created intertidal reef in the Yangtze River estuary, China.…”

Effects of oyster harvest activities on Louisiana reef habitat and resident nekton communities

“…Oysters are commonly acknowledged as ecosystem engineers of shallow-water estuaries. Oysters modify the local environment by providing refuge and foraging habitat (Peterson et al, 2003;Coen et al, 2007), by altering local hydrodynamic processes (Lenihan, 1999), and by affecting local water quality (Newell et al, 2005;Piehler and Smyth, 2011;zu Ermgassen et al, 2013). Globally, more than 85% of oyster reefs have been identified as functionally extinct; disease, poor water quality, and destruction of the physical habitat have been identified as the major proximate causes (Beck et al, 2011).…”