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Although seagrass meadows form a relatively homogenous habitat, escarpments, which form three‐dimensional structures and originate from the erosion of seagrass peat, can provide important habitat for reef fishes. Here, we compare fish assemblages and habitat structural complexity among seagrass Posidonia australis escarpments and canopies, as well as limestone reef habitats, to understand the role of seagrass escarpments as reef fish habitat in Shark Bay, Western Australia. The total number of fish species, fish biomass, and top predator biomass were significantly higher in seagrass escarpments and reef habitats than in seagrass canopies due to lower habitat structural complexity and thus becoming suitable habitats for predators and prey in the latter. Both seagrass escarpment and reef habitats host similar assemblages of top predators and carnivorous fishes, such as Epinephelus coioides, Microcanthus strigatus, and Choerodon schoenleinii, that were absent in seagrass canopies. Seagrass escarpments provide an alternative habitat for reef fishes comparable to rocky reefs, which are limited in Shark Bay. Caves and ledges within the escarpments support 13.4 Mg of fish and 3.6 Mg of top predator species of commercial interest within the Shark Bay World Heritage Site. Additional research is needed to further understand the ecological importance of seagrass escarpments in enhancing fish biomass and biodiversity, as reproduction grounds or refuge from predators, and to investigate the role of meadow edges in ecosystem function. [ABSTRACT FROM AUTHOR]

Key to understanding the impacts of invasive macroalgae on local food webs is determining the extent to which native herbivores consume the invasive macroalga. We used multiple-choice feeding assays to ascertain the relative feeding preferences of four subtidal grazers (the amphipod Aora typica, the isopod Batedotea elongata and the gastropods Cookia sulcata and Haliotis iris) for the invasive macroalga Undaria pinnatifida and six native macroalgae (Macrocystis pyrifera, Durvillaea antarctica, Carpophyllum flexuosum, Cystophora scalaris, Marginariella boryana and Ulva spp.) that are all abundant along the Otago coast of southern New Zealand. Multiple-choice feeding assays were run under laboratory conditions during the austral autumn (April and June) of 2013. The relative abundances of the macroalgae in the field were also determined. All of the grazers ate U. pinnatifida at rates comparable to most of the native macroalgae, except for B. elongata, which barely consumed it. This indicates that U. pinnatifida, which was shown to be more abundant than native macroalgae in subtidal habitats, has the potential to contribute organic matter to the local food web and may be an undesirable food for some group of grazers. We suggest that U. pinnatifida could potentially alter existing trophic relationships., Author(s): Rocio Suarez Jimenez[sup.1], Christopher D. Hepburn[sup.2], Glenn A. Hyndes[sup.3], Rebecca J. McLeod[sup.4], Richard B. Taylor[sup.5], Catriona L. Hurd[sup.1] [sup.6] Author Affiliations: (1) Department of Botany, University of Otago, 9054, [...]

Sandy beaches are iconic interfaces that functionally link the ocean with the land via the flow of organic matter from the sea. These cross‐ecosystem fluxes often comprise uprooted seagrass and dislodged macroalgae that can form substantial accumulations of detritus, termed 'wrack', on sandy beaches. In addition, the tissue of the carcasses of marine animals that regularly wash up on beaches form a rich food source ('carrion') for a diversity of scavenging animals. Here, we provide a global review of how wrack and carrion provide spatial subsidies that shape the structure and functioning of sandy‐beach ecosystems (sandy beaches and adjacent surf zones), which typically have little in situ primary production. We also examine the spatial scaling of the influence of these processes across the broader land‐ and seascape, and identify key gaps in our knowledge to guide future research directions and priorities. Large quantities of detrital kelp and seagrass can flow into sandy‐beach ecosystems, where microbial decomposers and animals process it. The rates of wrack supply and its retention are influenced by the oceanographic processes that transport it, the geomorphology and landscape context of the recipient beaches, and the condition, life history and morphological characteristics of the macrophyte taxa that are the ultimate source of wrack. When retained in beach ecosystems, wrack often creates hotspots of microbial metabolism, secondary productivity, biodiversity, and nutrient remineralization. Nutrients are produced during wrack breakdown, and these can return to coastal waters in surface flows (swash) and aquifers discharging into the subtidal surf. Beach‐cast kelp often plays a key trophic role, being an abundant and preferred food source for mobile, semi‐aquatic invertebrates that channel imported algal matter to predatory invertebrates, fish, and birds. The role of beach‐cast marine carrion is likely to be underestimated, as it can be consumed rapidly by highly mobile scavengers (e.g. foxes, coyotes, raptors, vultures). These consumers become important vectors in transferring marine productivity inland, thereby linking marine and terrestrial ecosystems. Whilst deposits of organic matter on sandy‐beach ecosystems underpin a range of ecosystem functions and services, they can be at variance with aesthetic perceptions resulting in widespread activities, such as 'beach cleaning and grooming'. This practice diminishes the energetic base of food webs, intertidal fauna, and biodiversity. Global declines in seagrass beds and kelp forests (linked to global warming) are predicted to cause substantial reductions in the amounts of marine organic matter reaching many beach ecosystems, likely causing flow‐on effects for food webs and biodiversity. Similarly, future sea‐level rise and increased storm frequency are likely to alter profoundly the physical attributes of beaches, which in turn can change the rates at which beaches retain and process the influxes of wrack and animal carcasses. Conservation of the multi‐faceted ecosystem services that sandy beaches provide will increasingly need to encompass a greater societal appreciation and the safeguarding of ecological functions reliant on beach‐cast organic matter on innumerable ocean shores worldwide. [ABSTRACT FROM AUTHOR]

The use of geostatistical indices to examine fishery-dependent data over time is novel. We assess the value of a range of these indices for describing trends in boat-based recreational fishing in Western Australia and areas of high effort and catches for two demersal species with varying biological characteristics, life histories and distributions. The number of blocks (10-× 10-nautical mile (~19-× 19-km) area) visited decreased by 40%, while the number of fishing trips with demersal species catch increased by 15%. Spatial indices showed a south-easterly shift in demersal catch per unit effort (CPUE) across survey years. The southerly shift of West Australian dhufish (Glaucosoma herbraicum) CPUE and subsequent return to the north likely to reflect the response of this temperate species to a marine heatwave. In comparison, CPUE of retained Baldchin groper (Choerodon rubescens) shifted north, whereas released catches shifted south with high probabilities of hotspots present associated with habitat structure. We identified hotspots of retained and released CPUE, highlighting potential areas where species experience high post-release mortality through barotrauma, and targeted spatial management strategies. Spatial indices allow quantitative definition of the structure of the fishery, identify high catch areas, and assess changes over time at a broader scale to sustainably manage multispecies fisheries. [ABSTRACT FROM AUTHOR]

Evaluation of fisheries management and sustainability indicators can be supported by a reliable index of harvest rate. However, the most appropriate model that accounts for recreational fisheries is largely unknown. In order to adjust for these factors, generalized linear models were applied to data from shore-based recreational fishing surveys conducted in Western Australia between 2010 and 2016. Five candidate error distributions (lognormal, Gamma, Zero-Altered Gamma, Tweedie, and delta-lognormal) and seven independent variables (year, month, target species, fishing platform, fishers' avidity, time of day, and day type) were examined for commonly caught nearshore teleost species. Zero-Altered Gamma and Tweedie models performed best overall, although model performance and explanatory variables varied between species. Standardized harvest rates for Australian herring (Arripis georgianus) declined from 1.88 ± 0.17 (mean ± s.e.) fish per fishing party per day) in 2010 to 0.86 ± 0.07 in 2016, while harvest rates for School whiting (Sillago spp.) increased from 0.44 ± 0.21 in 2010 to 0.94 ± 0.34 in 2016. The standardized harvest rates for both species generally showed less fluctuation among years and consistently had smaller errors than the raw harvest rates. Overall, the results suggest that the choice of error distribution, as well as explanatory variables, is species dependent when assessing shore-based fisheries. The approach used could easily be adapted to other recreational fisheries to establish reliable species-specific harvest rates that can detect variability against thresholds set in harvest strategies. [ABSTRACT FROM AUTHOR]

Food webs on ocean-exposed sandy beaches are almost entirely underpinned by trophic subsidies from the sea. Ghost crabs (Ocypode spp.), which are highly mobile invertebrate consumers that display a diversity of feeding modes, form an important consumer on numerous beaches around the world. However, little is known of their trophic structure and the role they play as vectors for spatial subsidies through movement of marine derived nutrients inland. The aim of this study was to determine the trophic ecology of the Golden ghost crab (Ocypode convexa) and understand what its role is in terms of marine connectivity along the mid-west coastline of Australia. Based on stomach content (percentage frequency (%F) and percentage volume (%V)) and stable isotope analyses (mixing models using ẟ13C and ẟ15N), the dietary composition of O. convexa was typically dominated by brown algae, and complemented by marine and terrestrial vascular plants and arthropods (various insects and amphipods). However, feeding assays revealed that the species had a clear preference for fish and invertebrate carcasses when the choice was offered, indicating a proclivity for the more nutritionally valuable animal flesh when available. Thus, ghost crabs are likely to be unenthusiastic consumers of vegetables, and are likely to feed on algae and macrophyte matter only when animal carrion or live animal prey is sparse. Consistent intake and assimilation of marine matter by ghost crabs, and their likely predation by higher level consumers, such as foxes (e.g. Vulpes vulpes) and birds (e.g. Corvus coronoides), support the concept that they form a vector for cross-boundary fluxes of marine carbon to inland ecosystems, although it needs to be recognized that ghost crabs also derive part of their nutritional requirements from terrestrial sources. Image 1 [ABSTRACT FROM AUTHOR]

The surf zones of ocean beaches provide habitat for a diversity of fishes and are prime sites for recreational angling and commercial net fisheries. Here, we review the global literature (152 studies) on surf fish ecology to better inform fisheries management and coastal conservation planning. These studies suggest that surf zones support diverse fish assemblages, which are characterized by high numerical dominance (10 species typically comprise 95% of catches), but also show that few families are especially common. The composition of assemblages is highly variable, changing with fluctuations in water temperature, wave climate and the biomass of drifting algae or seagrass. Fish use surf zones as feeding habitats and transit routes, but these areas might not be widely used as spawning sites or juvenile nurseries. These systems are under escalating human pressures, most notably from coastal urbanization and recreational angling. Despite the recognized ecological and economic importance of surf-zone fishes, few studies have tested for impacts of urbanization or fishing. The benefits of marine reserves for fish in surf zones are also rarely measured. We suggest that progress will be made by moving from largely descriptive studies to hypothesis-driven research, which is guided by contemporary ecological theory and adapts modern techniques from research in other ecosystems. A key challenge is to obtain empirical data that are needed to improve the effectiveness of fisheries management and underpin conservation planning for coastal waters. [ABSTRACT FROM AUTHOR]

The transfer of organic material from one coastal environment to another can increase production in recipient habitats in a process known as spatial subsidy. Microorganisms drive the generation, transformation, and uptake of organic material in shallow coastal environments, but their significance in connecting coastal habitats through spatial subsidies has received limited attention. We address this by presenting a conceptual model of coastal connectivity that focuses on the flow of microbially mediated organic material in key coastal habitats. Our model suggests that it is not the difference in generation rates of organic material between coastal habitats but the amount of organic material assimilated into microbial biomass and respiration that determines the amount of material that can be exported from one coastal environment to another. Further, the flow of organic material across coastal habitats is sensitive to environmental change as this can alter microbial remineralization and respiration rates. Our model highlights microorganisms as an integral part of coastal connectivity and emphasizes the importance of including a microbial perspective in coastal connectivity studies. [ABSTRACT FROM AUTHOR]

The consequences of macroalgal invasions for coastal ecosystem structure and food webs remain poorly understood. We investigated the relative contribution of the invasive kelp Undariapinnatifida (Heterokontophyta), which has an annual life cycle, to the composition of algal assemblages in subtidal rocky reefs and in the wrack of nearby surf zones and sandy beaches in southern New Zealand. Undaria pinnatifida made substantial contributions to the density and percent cover (up to 75%) of algal communities in the subtidal habitats studied, suggesting that it influences the living habitat and food resources in subtidal temperate reefs. In comparison, its contribution to the drift in the surf zone and algal wrack that accumulated on sandy beach habitats was low (usually < 25%) compared with native kelps, although it occasionally contributed up to 75% of the drift biomass. This difference likely reflects the lack of buoyancy of U. pinnatifida compared with native kelp species, limiting its capacity to act as a vector for the transfer of carbon across coastal landscapes. In contrast to the native perennial algae, U. pinnatifida's contribution to algal communities in subtidal habitats was inconsistent through time, with the greatest percent cover in early summer (December) and the lowest in early winter (April). Such a temporal pattern in the biomass of wrack and drift U. pinnatifida in beach and surf-zone habitats was, however, less apparent. Our findings suggest that the strongly seasonal and highly invasive U. pinnatifida has the potential to influence carbon fluxes and faunal communities in subtidal food webs, but that such effects are unlikely to be transferred across coastal habitats. [ABSTRACT FROM AUTHOR]

To inform management, baseline ecological studies in estuaries must be implemented at spatial scales that accommodate both environmental gradients and likely anthropogenic pressures. We describe fine-scale spatial patterns in the abundances and size structure of large infaunal bivalves inhabiting shallow sand habitats in the lower reaches of a relatively undisturbed, permanently open, temperate estuary. Sampling over 3 years at 19 sites during the autumn, when freshwater influence was minimal, revealed that Soletellina alba, Wallucina assimilis and Paphies elongata were consistently the most abundant of nine species present. Although most abundant near the ocean entrance, S. alba was distributed widely and shells of differing lengths, and presumably ages, were present at most sites, suggesting that this species recruited continuously throughout the study area when conditions were appropriate. In contrast, W. assimilis and P. elongata occurred only near or in the entrance channel of the Nornalup Inlet in areas where seagrass rhizomes may grow and where oceanic influences caused relatively turbulent conditions, respectively. Sediment structure appeared to exert only a moderate and intermittent influence on the bivalve assemblage at some sites where particularly large grain sizes occurred. This study provides important baseline information on the distribution and abundance of large bivalves in this estuary. These species are likely to be important in the trophic ecology of this system and are potential indicators of disturbance and ecosystem health. Baseline ecological studies are important to inform the management of temperate estuaries. We describe patterns in the abundance and size structure of large bivalves inhabiting shallow sand habitats in a permanently open estuary. While bivalves are probably important in the trophic ecology of this system and are potential indicators of disturbance and ecosystem health, we highlight that effective management also requires knowledge of natural processes and anthropogenic pressures. [ABSTRACT FROM AUTHOR]

Abstract: Understanding variability in stable isotope abundance is essential for effective hypothesis testing and evaluating food sources, trophic levels and food web structure. The magnitude and sources of variability are likely to differ among taxonomic and functional groups. We aimed to quantify variability of δ13C and δ15N for 16 species representing seven distinct taxonomic groups of benthic invertebrates and autotrophs in a marine ecosystem. We quantified the magnitude of variability among individuals or shoots separated by metres, among eight sites separated by kilometres, and between two survey occasions separated by months. δ13C varied by as much as 7‰ for primary producers, 4‰ for consumers, while δ15N varied by as much as 9‰ and 2‰ respectively. Variation in δ15N of seagrass was largely accounted for by differences among sites, while variation in δ13C was mainly attributable to shoots collected a few metres apart. Compared to seagrasses, variation in macroalgae was mainly explained by differences between the two survey occasions for δ15N and among individuals collected a few metres apart for δ13C. Variation was generally lower for consumers and typically explained by differences among individuals for δ15N but displayed inconsistent patterns for δ13C. Dual isotope Bayesian mixing models showed that the potential contributions of food sources for herbivorous consumers varied among sites and between survey occasions, and also that there was high variability or uncertainty in the contributions of sources within sites. The relative consistency in the main sources of variation among broad taxonomic groups in autotrophs suggests that aspects of physiology that are phylogenetically conserved might be important influences on variation in natural abundances of stable isotopes. In comparison, the sources of variability were less consistent within and among broad consumer groups, suggesting complex interactions between consumers and their food sources. [Copyright &y& Elsevier]