AbstractCopepod carcasses and non‐predatory mortality can occur due to natural senescence, disease, pollution, and physicochemical stress. Our objective is to evaluate and characterize the rates of non‐predatory mortality and the contribution of zooplankton community carcasses, represented by the copepods, in tropical estuarine ecosystems with different degrees of urbanization. During the study, there was a significant difference between environments and copepod carcasses, with Suape Bay (moderately urbanized) being the environment with the highest abundance of adult copepod carcasses (93.3%). The average non‐predatory mortality rate of adult copepods was 0.15 day−1: Santa Cruz Channel (sparsely urbanized) contributed the lowest values, with a mortality rate of 0.01 day−1, and Suape (moderately urbanized) had the highest rate (2.80 day−1). The families Paracalanidae (0.554 day−1) and Oithonidae (0.122 day−1) had the highest values, with an average carcass decomposition of 4.7 days. Among the environments studied, there was little differentiation between carcass percentages and mortality rate, not supporting the hypothesis that the higher rates of mortality among non‐predatory copepods were related to large urban centers. However, there was an almost proportional contribution of carcasses and non‐predatory mortality in all but a few areas, agreeing with the hypothesis that there is spatial variation with respect to carcasses in tropical estuaries. With our work, we show that estuaries can provide the estuarine food web with a significant portion of copepod carcasses, which may vary by family, and that it is not necessarily environments with a higher degree of urbanization that will have higher mortality rates.

AbstractCertain aspects of meiobenthos research are given detailed and comprehensive attention in Chapter 7 (Hidden players: meiofauna mediate ecosystem effects of anthropogenic Disturbances in the ocean) of the Springer publication ‘New Horizons in Meiobenthos Research; Profiles, Patterns and Potential’ (O. Giere & M. Schratzberger (Eds.). This book review is concerned solely with Chapter 7 which underlines the view that meiofaunal species play a very important part as hidden players in the impacts of anthropogenic disturbances in the ocean, an aspect justifiably arousing global concerns. The chapter constitutes a veritable compendium where much that was previously unsuspected in those ‘untouched reaches’, is revealed under the scrutiny of its many internationally known authors. Of its ten sections, eight deal consecutively with the impact of disturbances caused by anthropogenic activities such as bottom fishing, pollution from organic sources, hydrocarbons, oil and chemical impacts, invasive species and climate change, followed by a section on the resilience of the meiofauna to such disturbances and the scale of their responses, with a final section outlining a forward perspective for future research. In addition, Chapter 7 contains an extensive bibliography which itself constitutes an important reference resource for researchers.

AbstractAscidians are sessile marine invertebrates found all over the world in a variety of natural and artificial habitats. The objective of this study was to provide the first inventory of ascidian diversity and abundance in North Carolina (NC) seagrass meadows. Eight sites along the NC coast were surveyed in May and June 2021 and at each site, 20 quadrats were deployed. All ascidian species within the quadrats were counted and identified based on morphological characterization and sequencing of the barcoding gene. Seagrass percent cover, biomass, and shoot density were also quantified. Ascidians were found in six sites and four species were recorded: the solitary species Molgula manhattensis, Styela plicata, and Bostrichobranchus sp., and the colonial Didemnum lutarium. Colonial specimens were generally attached to hard substrate, while solitary species were often found attached to seagrass rhizomes and leaves. S. plicata and M. manhattensis haplotype diversity were equivalent to previous descriptions from individuals collected on artificial substrates and other locations. Ascidian abundance was positively correlated with seagrass biomass but not with seagrass percent cover. A fifth species, the solitary Styela canopus, appeared in a site revisited in October 2021. Temperate ascidians are known to have seasonal cycles, thus further research should include monthly surveys to assess ascidian diversity and abundance over time.

AbstractAscidians are rapidly emerging biofouling organisms that generally occur on the natural and artificial substratum of the marine environment. However, very few studies have been reported on their species diversity and distribution patterns. This present investigation focuses on the seasonal impact on ascidians diversity. The distributions of ascidians were recorded by the collection of samples in six sampling stations from Andaman and Nicobar Islands. A total of 43 species of ascidians (32 colonial, 11 solitary) were recorded and most of the species are under the Didemnidae family. Various diversity indexes were utilized to examine the diversity, richness and evenness of species and to look at the assorted variety among tests and their likeness regarding species composition. The greatest (3.227) individuals were observed during summer season in Pigeon Island and the lowest (2.063) number of species were recorded during the monsoon season in Haddowharf harbour. The Margalef richness (d) fluctuated between in the range of 2.033 and 5.53 during the monsoon in Haddowharf harbour and Carbyns Cove beach in summer seasons. The Pielou's evenness record (J′) changed from 0.7409 to 0.9713. Diversity indexes were recorded as followed the order of 0.9642, 0.9552, 0.9482 and 0.9292 at Carbyns Cove shoreline, Burmanella, Pigeon Island and Campbell Bay individually during summer season. Present findings in the cluster examination uncovered that the species at various stations have framed four gatherings. Most elevated species rates were spread in summer. Field observation shows that species distribution is able to tolerate temperature ranges of 26.9–30.3°C and salinity of 32.1–34.64 ppt. Occasional examples of space occupation by colonial ascidians corresponded with seasonal changes in seawater temperature and salinity.

AbstractAnthropogenic impacts on coastal habitats can result in alterations of diversity parameters in marine invertebrate assemblages. Macroalgae beds are highly susceptible to human‐induced disturbances, supporting a great diversity of molluscan species and being ecologically important for coastal ecosystems. This study investigates the diversity alterations on Sargassum‐associated molluscan assemblages from areas with different distances from a main source of pollution within a historically impacted bay in Brazil. In general, sites closer to the pollution source presented lower species diversity, trophic diversity, and taxonomic relatedness among species. Beta diversity among assemblages was highly correlated with environmental differentiations among localities due to heavy metal concentrations in algal tissue. Bittiolum varium was the dominant species and was mainly responsible for differences in community parameters. Several trophic groups were well‐represented in Sargassum‐associated molluscan fauna, but assemblages were mostly dominated by micrograzers. A seasonal trend was observed in diversity alterations, with lower diversity during warm season at most sites except Santa Rita, possibly because it is the site less affected by human impacts. The importance of other environmental variables, such as hydrodynamism, for molluscan composition is also discussed. Our results highlight the potential of Sargassum‐associated molluscan assemblages for the study of impacted areas and reinforce the importance of using multiple community metrics to understand the biodiversity patterns of marine invertebrates under anthropogenic impacts.

AbstractDuring a cold La Niña period (August 2007–January 2008) in the central Galápagos archipelago, 70% of Pocillopora branching corals were severely bleached across three long‐term monitoring sites, affording an opportunity to examine its impact on the persistence of these corals and their associated community of fish and mobile macroinvertebrates. Using a time series empirical approach, we tagged and tracked the fate of 96 coral heads and their associates. When surveyed in July 2008, recovered live and dead corals that were previously severely bleached supported similar levels of species richness (randomized observed and estimated Chao 1). By contrast, richness on the surviving live corals remained fairly stable, while Chao 1 estimated richness on dead corals underwent a nearly 50% increase between July and January 2009, thereafter declining to 50% of originally surveyed richness by February 2010. This nonlinear change in species richness was largely due to an influx and decline in opportunistic generalists including pencil urchin bioeroders, gastropod snails, and hermit crabs that colonized dead corals and fed on sessile invertebrates and algae that had initially recruited to dead and undefended coral substrate. Thus, dead corals retained high overall species richness until live corals had recovered, after which richness declined as dead corals eroded and disintegrated (July 2011). Live corals attracted a less speciose but stable assemblage of mutualistic xanthid crabs and fishes that increased in abundance over time with the recovery and growth of live coral tissue. Overall, coral status (live/dead), planar area and maximum branch length predicted the number of species associated with each colony. The delayed diversity loss of associated species following La Niña disturbance to a foundation species represents a local extinction debt of 32–49‐month duration. A better understanding of the scale of extinction debt in foundational marine ecosystems is needed to quantify the breadth of impacts of climate oscillations on biodiversity and ecosystem functioning.

AbstractBecause foundation species create structure in a community, understanding their ecological and evolutionary responses to global change is critical for predicting the ecological and economic management of species and communities that rely on them. Giant kelp (Macrocystis pyrifera) is a globally distributed foundation species with seasonal fluctuations in abundance in response to local nutrient levels, storm intensity, and ocean temperatures. Here we examine genetic variation in individual and population‐level responses of early life history stages (zoospore settlement, survival, and gametogenesis) to increased temperatures to determine the potential for natural selection on temperature‐tolerant individuals that would allow adaptation to a changing climate. We collected fertile M. pyrifera sporophyll blades from three sites along the California coast (Los Angeles, Santa Barbara, Monterey Bay) and induced zoospore release in the lab. Spores settled on microscope slides at three treatment temperatures (16, 20, and 22°C), matured for 21 days, and were imaged weekly to determine settlement, survival, and maturation success. On average, individuals from all sites showed lower rates of settlement and maturation in response to increasing temperature. However, the magnitude of the responses to temperature varied among populations. Survival tended to increase with temperature in Los Angeles and Santa Barbara populations but decreased with increasing temperature for the Monterey Bay population. We observed little genetic variation in temperature responses among individuals within sites, suggesting little scope for evolution within populations to increase the resilience of M. pyrifera populations to warming ocean temperatures and predicted declines in kelp abundance. Yet sufficient dispersal among populations could allow for adaptation of early life history traits among populations via evolutionary rescue of declining populations.

AbstractTool use is a remarkable animal behaviour, and the investigation of this phenomenon in fishes is a relatively new and growing field. The graphic tuskfish Choerodon graphicus (De Vis 1885) has previously been documented using anvils but the extent and variability of this tool‐use behaviour remains poorly understood. In this study, we investigated whether C. graphicus breaks open crustaceans and/or sea urchins on anvils in different microhabitats and/or locations. We also inspected two previously identified anvils for evidence of long‐term anvil use. Three individual C. graphicus were observed breaking open sea urchins on dead coral anvils in a coral rubble microhabitat at Île aux Canards, New Caledonia. They produced visual and auditory cues while carrying out tool‐use behaviour and these cues often attracted attendant fishes. Notably, two anvils appeared to have been used by one or more tool‐using C. graphicus for years at Îlot Maître, New Caledonia. These findings suggest that tool‐use behaviour is both innate and learned and is a prey‐handling method of choice used by individuals that learn to specialise in large prey items from a few underutilised hard‐shelled prey species. Furthermore, the findings show that specific anvils can be used long‐term and also suggest that individual wrasses may carry out tool‐use behaviour long‐term. The study provides new insights into the feeding ecology and social behaviour of C. graphicus and underscores the need to further investigate the extent and variability of tool use in fishes.

AbstractMarine mesograzers use macroalgae as food and habitat and may have strong top‐down effects on plants and macroalgae. Sympatric mesograzer species often differ regarding host use and feeding behavior, which may lead to distinct impacts by these consumers on primary producers. The amphipods Hyale niger and Ampithoe marcuzzii are mesograzers abundant that co‐occur in Brazilian waters and, although they use several macroalgae as habitat, it is unknown how much the food value of these hosts explains the host use pattern by the two mesograzers. Herein, we investigated the abundance and feeding behavior of the sympatric amphipods H. niger and A. marcuzzii. For that, their abundance on the macroalgal hosts Sargassum filipendula, Padina gymnospora, and Dichotomaria marginata was evaluated seasonally in a rocky shore at Fortaleza Beach, state of São Paulo, Brazil. Also, multiple‐choice and no‐choice feeding experiments were carried out at laboratory to evaluate the feeding behavior of these mesograzers. The abundance of H. niger was similar among the three macroalgal hosts (except during winter), while A. marcuzzii was more abundant on Dichotomaria and Padina than Sargassum in all seasons. Moreover, H. niger consumed more Padina than Dichotomaria and Sargassum in both feeding experiments. In turn, A. marcuzzii preferred to feed on Padina when it had a choice and consumed the three macroalgal hosts at similar levels in the no‐choice feeding experiment. Overall, H. niger and A. marcuzzii differ from each other regarding their feeding behavior and host use pattern. In particular, the food value of macroalgae seems to partially explain the host use by A. marcuzzi, but not by H. niger. The differences between H. niger and A. marcuzzii may result in varying impacts on primary producers.