Effect of green macroalgal blooms on the behavior, growth, and survival of cockles Clinocardium nuttallii in Pacific NW estuaries

Abstract

Nutrient over-enrichment can produce adverse ecological effects within coastal ecosystems and negatively impact the production of ecosystem goods and services. In small estuaries of the U.S. Pacific Northwest, seasonal blooms of green macroalgae (GMA; Family Ulvaceae) are primarily associated with natural nutrient input, rather than anthropogenic sources. This provided us a unique opportunity to investigate the effects of naturally-stimulated macroalgal blooms on intertidal bivalves. (heart cockles) are an important species for shellfisheries in the region. In summer population surveys, we found that cockles emerged from the sediment with greater frequency as GMA biomass increased. Experimental manipulation of GMA biomass in the field showed that GMA elicited emergence, evoked above-ground lateral movement, inhibited shell growth, and increased mortality (by 34.0 ± 15.2%) in cockles. Laboratory experiments revealed that the interaction of a weighted barrier at the sediment surface and GMA presence elicited rapid emergence among cockles. Risk assessment of the emergence response in cockles showed that the emergent population experienced 11.0 ± 8.0% mortality due to gull predation, while laboratory exposure to elevated temperatures (≥34 °C) slowed valve-closure, inhibited reburial, and increased mortality, which could have translated to 7.1 ± 1.5% mortality. We found that cockles avoided mortality due to burial below GMA mats by emerging from the sediment, but that behavior consequently put them at risk of mortality due to heat stress or gull predation. Regardless of nutrient source, our research showed that GMA blooms pose a threat to the survival of intertidal bivalves.

Ecological Mechanisms Underpinning Ecosystem Service Bundles in Marine Environments – A Case Study for Shellfish

“…Stressors generally have a negative impact on survival rates. For example, emergence of infaunal shellfish from the sediment when stressed by macroalgal blooms or hypoxia, and physical distress from high temperatures can alter mortality rates (Lewis and DeWitt, 2017). Disease outbreaks (Wilkie et al, 2013) can affect survival rates of farmed and wild shellfish populations, but also could make them unsafe for harvest and human consumption, thereby resulting in a loss of value.…”

Estimating the distribution of harvested estuarine bivalves with natural-history-based habitat suitability models

“…We conducted an extensive review of literature (predominantly from NE Pacific estuaries, including the U.S. PNW) on the natural-hi story, distribution, and physiology of the five bayclam species (Clinocardium nuttallii, Mya arenaria, Tresus capax, Saxidomus gigantea, and Leukoma staminea) to obtain information on species-specific sensitivities (i.e., survival, mortality, presence-absence) to several environmental variables (see Appendix 2). Although many environmental variables can affect the spatial distribution of bivalves within an estuary, particularly during short-term events (e.g., green macroalgal bloom effects on cockles; Lewis and DeWitt, 2017), four variables that were consistently cited as influential on survival and distribution were: bathymetric depth, sediment silt-clay %, low salinity, and the presence of burrowing shrimp. Henceforth, these are the "habitat variables" used in FISBHE.…”

“…Physical sediment characteristics are important to bay-clams because these species are infaunal, meaning most of their lifetime is spent within the sediment. For instance, T. capax prefers stable, consolidated sediment (characteristic of fine mud or clay) because it is a sedentary deeper-lived species (Lauzier et al, 1998;Dethier, 2006), whereas C. nuttallii is a more mobile species (Lewis and DeWitt, 2017) that often inhabits unconsolidated surface sediments (sandy or mixed sediments) (Gaumer and McCrae, 1990;Dethier, 2006) better suited for active movement. Extended periods of low salinities are limiting to these bivalve species (Gaumer and McCrae, 1990;Lauzier et al, 1998;Endreny and Sylvia, 2006;Dethier, 2006;Rudy et al, 2013).…”

Living under Ulva canopy: The case of the scavenger snail Buccinastrum deforme in a eutrophic macrotidal bay in Patagonia (Argentina)

“…The detrimental effects of macroalgal blooms due to nutrient enrichment have been demonstrated by many studies, including negative effects both on natural communities and ecosystem functions (Fox et al, 2009; Lewis & De Witt, 2017; Österling & Pihl, 2001; Valiela et al, 1997) and on the goods and services of human use (Jessen et al, 2015; Lyons et al, 2014; Troell et al, 2005). Eutrophicated systems with a large water exchange (i.e., macrotidal) or at initial stages of eutrophication, however, can have positive effects on communities (Baldrighi et al, 2019; Becherucci et al, 2021; Martinetto et al, 2010; Quillien et al, 2015).…”