Search

Foundation species are spatially dominant species that increase habitat complexity and provide substrate and shelter for many smaller species. Through a mensurative field experiment, we tested the hypothesis that functional aspects of the associated communities are related to structural and functional properties of the foundation species. Specifically, we contrasted invertebrate communities living in mussel (Mytilus) and seaweed (Chondrus) stands from the same rocky intertidal environments in Atlantic Canada. Both stands reach similar heights above the substrate, but they differ structurally (rigid mussel shells vs. flexible seaweed fronds) and functionally (mussels generate biowaste while seaweeds offer food for herbivores). Our data supported the hypothesis in various ways. Detritivory (mostly by oligochaetes) was more prevalent in mussel stands, while herbivory was more prevalent in seaweed stands. Predators were mostly mites and, consequently, they were more prevalent in mussel stands, as mites eat oligochaetes. Functional traits related to body and mobility types were also related to properties of the foundation species. Overall, we conclude that structural and functional properties of foundation species can predict functional aspects of the associated communities. This concept may help to develop effective restoration strategies after the loss of foundation species due to anthropogenic factors. [ABSTRACT FROM AUTHOR]

This article discusses the mass disappearance of intertidal mussels in eastern Canada after an unusual winter cold snap in February 2023. The decline in mussel abundance is concerning due to its impact on coastal biodiversity. The cold snap, which saw temperatures drop below -20°C, is believed to be the main driver of the mass disappearance. Other factors such as predation, ice scour, and wave action were ruled out as causes. The article highlights the potential implications of climate change on the future of coastal ecosystems and emphasizes the need to study the frequency of extreme weather events. [Extracted from the article]

Shallow coastal environments are becoming more susceptible to marine heatwaves, particularly in Atlantic Canada, which is experiencing higher rates of ocean warming compared with the global average. Understanding bivalves' tolerance to heatwaves in Atlantic Canada is especially important, given the magnitude of bivalve aquaculture in this region. In this study, the physiological state of four commercially important bivalve species—blue mussel (Mytilus edulis Linnaeus, 1758), eastern oyster (Crassostrea virginica (Gmelin, 1791)), soft shell clam (Mya arenaria Linnaeus, 1758), and hard clam (Mercenaria mercenaria (Linnaeus, 1758))—was observed during a naturally occurring heatwave in Prince Edward Island, Canada. The metabolism, feeding physiology, and scope for growth of each species were compared. Results from this study, and comparisons with the literature, show interspecific variability in the metabolic rate and feeding physiology between species, but generally oysters, soft shell clams, and hard clams were less impacted during the heatwave compared with the blue mussels. Additionally, only the scope for growth of mussels declined throughout this experiment, which may be explained by cumulative heat stress, as temperatures experienced during this heatwave exceeded the thermal tolerance limits of mussels. [ABSTRACT FROM AUTHOR]

Abstract: This study examines the effect of mussel farming on benthic infaunal communities in baie de Gaspé, eastern Canada, at two spatial scales: 10m (directly under vs. between mussel longlines — Position) and 100m (between mussel farm and reference locations — Treatment, each of which was replicated at 4 Sites). None of the evaluated univariate descriptors of benthic communities (abundance, taxonomic richness, Shannon–Weiner diversity, AMBI, and M-AMBI) differed between Treatments or among Positions within Sites in any consistent way. Similarly, multivariate community structure also did not differ among Treatments. In contrast, multivariate community structure directly under mussel lines differed from that between mussel lines in 3 of 4 mussel farm sites whereas none of the reference sites showed such 10m-scale variation. Of the species that accounted for the greatest proportion of the dissimilarity between Positions within mussel farm sites, second-order opportunistic species (Prionospio steenstrupi and Pectinaria granulata) were consistently more abundant directly under mussel lines than between them. Species belonging to other ecological groups did not show any consistent trends. It is suggested that studies that do not consider within-site (10m-scale, below vs. between longlines) variation may fail to detect the influence of suspended bivalve culture in some cases. Overall, effects of mussel culture in baie de Gaspé were slight and within the natural variation of benthic communities in the area. This suggests that the current industry should be sustainable. However, plans to expand the industry in the region remain to be evaluated with respect to the ecological carrying capacity of the entire bay. [Copyright &y& Elsevier]

Abstract: Previous studies have suggested that a large proportion of the more heterozygous mussels are lost while in suspension culture. Such a reduction in multi-locus heterozygosity (MLH) could impact mussel production because more heterozygous individuals have better growth and survival than more homozygous ones. The present study followed the changes in MLH over a year in two different cohorts and found a reduction in MLH during the culture cycle for both cohorts. This reduction did not occur during the early phases of the culture operations, such as sleeving (= socking), or during the first weeks in suspension culture, but took place during the following growing season starting in early summer for both cohorts. The MLH decrease was not associated with different environmental conditions at the growing site. It is hypothesized that mussels characterized by high MLH are more mobile than those with lower MLH and migrate out of the mesh tubes faster after sleeving to get access to better growing conditions (space and food). However, being at the periphery of the sleeves, these more heterozygous individuals are more vulnerable to fall-offs due to turbulence and/or self-thinning. We suggest that the MLH decrease on the sleeves is not caused by the selective mortality of more heterozygous individuals but rather by higher losses through fall-offs. [Copyright &y& Elsevier]

Abstract: This paper describes the historical development of blue mussel (Mytilus edulis) farming in Tracadie Bay (Prince Edward Island, Canada) and relates the spacing of suspended sleeves (S S) on longlines to seston uptake. From 1990 to 2001, mussel biomass in Tracadie Bay increased by a factor of four (from 1137 to 4743 t). By 2001, seston uptake rates were approximately three-fold water renewal rates, and harvest yields (kg sleeve−1) were significantly lower than in the early 1990s. A one-year field experiment was carried out to determine whether a change in S S could restore harvest yields. We found that S S (10, 20, 40, 60, 80 cm) had no significant effect on the condition index of mussels. However, high S S positively affected shell growth and abundance for small seeds that were densely packed within sleeves. A complete husbandry shift toward high S S and high seeding densities (within sleeves) may enhance farm productivity (production per unit of effort) and curtail seston uptake at the bay scale. [Copyright &y& Elsevier]

Aim We performed the first test of predictions from the abundant-centre model using north-west Atlantic coastal organisms. We tested the hypotheses that the density of intertidal mussels (Mytilus edulis and M. trossulus) and dogwhelks (Nucella lapillus) and mussel age and size would peak at an intermediate location along their distribution range. We also assessed the latitudinal variation in critical aerial exposure time. Location North-west Atlantic coast between Newfoundland (Canada) and New York (USA), covering 1800 km of shoreline. Methods Using a nested design, we measured mussel density, age and size and dogwhelk density in 60 wave-exposed rocky intertidal sites spread evenly in six regions. Critical aerial exposure times were determined using online data. Results Mytilus edulis peaked in abundance in Maine and was much less abundant in the other regions. Mytilus trossulus peaked in abundance in southern Nova Scotia and Maine, was less abundant in the other regions to the north, and was absent in the southernmost region (New York). Both mussel species were least abundant in a northern region (Cape Breton), although not in the northernmost region (Newfoundland). Critical aerial exposure times were negatively correlated with overall mussel density. Mussel age and size were similar among regions. Dogwhelks peaked in abundance in Maine and were much less abundant in the other regions, being positively correlated with overall mussel density across regions. Main conclusions Density data for M. edulis and N. lapillus provide limited support for an abundant-centre pattern, while M. trossulus shows a clear rampedsouth distribution. Critical aerial exposure times suggest that physiological stress during summer and winter low tides may be lowest in Maine and southern Nova Scotia, which might partially explain mussel predominance in those regions. Winter ice scour in Cape Breton may explain the abundance trough observed there. Mussel size and age may be more limited by wave exposure at our sites (as they all face open waters) than by regional differences in environmental stress. Dogwhelks, which prey on mussels, seem to respond positively to prey density at the regional scale. Our study supports the notion that, while the abundant-centre model is a useful starting point for research, it often represents an oversimplification of reality. [ABSTRACT FROM AUTHOR]

Blue mussels, Mytilus edulis, and sea stars, Leptasterias polaris, were collected in September 1995 at 8 stations along the south shore of the St Lawrence Estuary for analysis of butyllins by GC-MS. Tributyltin CM, dibutyltin (DBT), and monobutyltin (MBT) found in mussels averaged 16, 32, 30 ng Sn g-1, respectively, indicating a low, but ubiquitous contamination of the St Lawrence Estuary shoreline.The very low TBT:DBT ratio (0.52) observed in mussel samples corresponds to the bioaccumulation of highly degraded butyltins present in suspended particulate matter at the end of the summer season. Total accumulated butyltins in sea stars feeding mussels reached 167 ng Sn g-1 in pyloric ceaca at station 8 near the Gaspe public wharf and five other stations had total Sn higher than 100 ng Sn g-1. Butyltin distribution in caeca and gonads of sea stars was different from mussels as the contribution of MBT was only 18% in L. polaris but reached over 38% in M. edulis. This difference may be attributed to the capability of sea stars to degrade and depurate organotins rapidly. [ABSTRACT FROM AUTHOR]