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Many marine habitats are at risk due to increasing frequency, intensity, and persistence of harmful algal blooms. Repeated cyanobacterial harmful algal blooms (cyanoHABs) in Florida Bay, USA, kill sponges, resulting in reduced filtration and loss of shelter for benthic species. The loss of these key ecosystem functions can impact disease dynamics if fewer pathogens are filtered from the water column (dilution), if shelter loss increases host density in remaining shelters and a directly transmitted disease is present (host regulation), or if shelter loss changes species distributions and foraging patterns (trophic exposure). We show persistent impacts to hard-bottom communities relative to non-impacted communities 2 yr after a significant cyanoHAB. We compared benthic structure, invertebrate epibenthic/infaunal community composition, and parasitism among macroinvertebrates, stone crab Menippe mercenaria , and Caribbean spiny lobster Panulirus argus . On sites degraded by cyanoHABs, we found more, smaller sponges, indicating regrowth. Despite this evidence of recovery, epibenthic/infaunal invertebrate communities were distinct and more diverse on unimpacted sites. Additionally, there were fewer, smaller bivalves on impacted sites. The bivalve Tucetona pectinata , prey for stone crabs, was nearly absent on impacted sites, resulting in decreased prevalence of the apicomplexan gregarine Nematopsis sp., which is trophically transmitted from T. pectinata to M. mercenaria . Panulirus argus virus 1 also appears to be affected by cyanoHABs, as it was absent on impacted sites but present in 26.5% of spiny lobster on unimpacted sites. Impacts remain evident 2 yr after significant cyanoHABs, which does not bode well for these areas considering the frequent reoccurrence of blooms.more » « less
The blue crab Callinectes sapidus is one of the most widely studied marine crustaceans due to its high economic value and ecological significance. Despite extensive research on the blue crab in North America, many questions remain about the distribution and abundance of the species in the subtropics and tropics. In many places, C. sapidus is sympatric with morphologically similar Callinectes spp., which has implications for seafood mislabeling. To enable rapid identification of the species, we designed and tested two PCR-based assays targeting the 12S rRNA mitochondrial gene. The first assay discriminates C. sapidus from other Callinectes spp. via post-PCR restriction digestion (PCR-RFLP) and the second assay discriminates among multiple Callinectes spp. through High Resolution Melting (HRM) analysis and supervised machine learning analyses. A total of 58 DNA samples from five Callinectes spp. (validated via 12S gene sequencing) were used for assay testing. The PCR RFLP assay was 100% accurate identifying C. sapidus from other Callinectes spp. HRM analysis of amplicons showed good discrimination among species, with distinct clusters formed between species with higher sequence homology. Linear discriminant analysis (LDA) classification of HRM curves was quite successful given the small dataset available, producing ∼90–91% mean accuracy in classification over all species with 100-fold cross validation. Much of the error came from misclassifications between C. similis and C. danae, which are ∼99% similar in sequence for the amplicon; collapsing them into a single class increased overall classification success to 94%. Error also arose from C. bocourti classifications, which had a reference set containing only three samples. Classification accuracy of C. sapidus alone via HRM was 97.5%. Overall, these assays show great promise as rapid and inexpensive methods to identify Callinectes spp. and have application for both ecological research and seafood identification or labeling.more » « less
Among the many Callinectes spp. across the western Atlantic, the blue crab C. sapidus has the broadest latitudinal distribution, encompassing both tropical and temperate climates. Its life history varies latitudinally, from extended overwintering at high latitudes to year-round activity in tropical locations. Callinectes sapidus reovirus 1 (CsRV1) is a pathogenic virus first described in North Atlantic C. sapidus and has recently been detected in southern Brazil. Little information exists about CsRV1 prevalence at intervening latitudes or in overwintering blue crabs. Using a quantitative reverse transcription PCR (RT-qPCR) method, this study investigated CsRV1 prevalence in C. sapidus across latitudinal differences in temperature and crab life history, as well as in additional Callinectes spp. and within overwintering C. sapidus . CsRV1 prevalence in C. sapidus was significantly correlated with high water temperature and blue crab winter dormancy. Prevalence of CsRV1 in C. sapidus on the mid-Atlantic coast was significantly lower in winter than in summer. CsRV1 infections were not detected in other Callinectes spp. These findings revealed that CsRV1 is present in C. sapidus across their range, but not in other Callinectes species, with prevalence associated with temperature and host life history. Such information helps us to better understand the underlying mechanisms that drive marine virus dynamics under changing environmental conditions.more » « less