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Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements.

Globally, key predators such as lobsters are thought to control urchins. In southeastern Australia, the role of Sagmariasus verreauxi (eastern rock lobster) as a key predator of the native urchin Centrostephanus rodgersii (long-spined urchin) has been questioned while the sympatric Heliocidaris erythrogramma (short-spined urchin) may be eaten more frequently. To test this, we tethered and filmed 100 urchins (50 C. rodgersii and 50 H. erythrogramma) outside of a lobster den over 25 nights to identify predators and quantify predation rates, time to feeding onset and handling time. Sagmariasus verreauxi exhibited very low predation rates (4%), despite being filmed walking past urchins repeatedly whereas Heterodontus galeatus (crested horn shark) was the main predator (45%). Predation rates by all predators (lobsters and sharks) were influenced primarily by tethering night but not urchin size or species. Predation increased throughout the study and while H. erythrogramma and C. rodgersii were eaten at similar rates, there was a trend for lobsters to eat H. erythrogramma and sharks to eat C. rodgersii. Feeding onset had no significant predictors though large C. rodgersii took longer to handle during feeding for both predators. Importantly, sharks readily consumed 25 C. rodgersii up to 121 mm Test Diameter (TD) while lobsters only ate one C. rodgersii (58 mm TD). These findings, although from only one test location, provide important insights into the species eating urchins and highlight the potential significance of overlooked predators such as H. galeatus. [ABSTRACT FROM AUTHOR]

Seagrasses provide critical ecosystem services such as carbon sequestration, sediment stabilisation and nursery habitat for juvenile fish. Zostera muelleri is ubiquitous within Australian and New Zealand estuaries, however, as a species is relatively understudied. We sourced seeds from a thermally affected east Australian estuary and investigated whether germination rates differed between ambient and thermally affected seeds over a variety of temperatures (16°C–28°C) to determine how seagrass systems might react in a warming climate. Germination for the experiment was low and totalled 5% of all seeds; however, similar numbers are typical in seed germination studies. Germination was highest at 16°C and was enhanced through the simulation of a 48‐h freshwater pulse. Thermally affected sites germinated faster and had greater mean maximum germination when compared to control sites regardless of experimental temperature. These findings indicate that Z. muelleri in this system may be exhibiting transgenerational plasticity due to the thermal stress the parent experiences. This result provides an alternate viewpoint to the current literature by suggesting that unknown transgenerational effects may provide Z. muelleri with greater germination plasticity against temperatures expected under predicted climate change scenarios than previously expected. [ABSTRACT FROM AUTHOR]

Worldwide, lobsters are considered key predators that control urchin populations. It has been widely reported that lobster size plays a significant role in the size of urchins they feed on, as does the size of the urchin. Generally, it is thought that small palinurid "spiny" lobsters measuring less than 120 mm carapace length (CL) are morphologically incapable of eating urchins, while large lobsters are voracious predators. Urchin size is expected to affect predation with larger urchins of greater than 90 mm test diameter (TD) presenting the most difficult prey. These generalities, however, have not been quantitatively tested for the eastern spiny lobster Sagmariasus verreauxi and recently the accepted size paradigm for lobsters eating urchins has come into question. The aim of this study was to assess whether lobster predation on urchins would differ with urchin size or species, or the size of lobster. Our results indicate that S. verreauxi does not fit the common lobster patterns regarding urchin predation. There were generally low rates of predation and a significant negative relationship between feeding and both lobster size and urchin size. We found that small lobsters were capable urchin predators with a higher likelihood of eating urchins than larger lobsters, which were more reluctant predators. While we did find the expected effect of smaller urchins being significantly more vulnerable prey, there was none of the expected size limitations for small lobsters eating large urchins and predation did not differ between urchin species, indicating that this was a general pattern. Overall, we observed low rates of predation, suggesting that either S. verreauxi may not be a key urchin predator like other lobster species elsewhere, or that small lobsters are underestimated as urchin predators in temperate marine ecosystems. [ABSTRACT FROM AUTHOR]

Globally, blue carbon ecosystems, including salt marsh, mangroves, and seagrasses, and the associated ecosystem services they provide, have declined substantially. In response, ecosystem restoration has recently increased but the scale and urgency of these activities has been limited by the lack of economic drivers. Herein, a multidisciplinary approach is presented that links hydrologic restoration with ecologic outputs to highlight the economic potential for commercial fisheries that could arise from restoring a drained floodplain. Initially, stable isotope models are used to predict the return of Eastern school prawn (approximately 300 kg yr−1 ha−1). Hydrologic models are then applied to determine the area of salt marshes and mangroves (over 2,000 ha) that could be potentially restored via tidal introduction. Together, these results indicate that ecological restoration in this region could contribute an annual benefit of approximately 230 tons of additional Eastern school prawn harvest, which could be valued at $3.1 ± 1.3 million AUD to commercial fisheries. This would represent a growth of nearly 50% from current annual harvest in the state. Given that this assessment excludes other values that would be gained, such as other species of fisheries value, carbon sequestration, biodiversity, and flood control, it represents a conservative financial estimate. Overall, this analysis highlights the scale of fisheries co‐benefits from tidal restoration projects, and how business cases for large‐scale blue carbon ecosystem restoration projects could be developed using multidisciplinary approaches. [ABSTRACT FROM AUTHOR]

The reduction of saltmarsh habitat at a global scale has seen a concomitant loss of associated ecosystem services. As such, there is a need and a push for habitat rehabilitation. This study examined an innovative saltmarsh restoration project in Australia which sought to address the threats of mangrove encroachment and sea level rise. The project was implemented in 2017, using automated hydraulic control gates, termed "SmartGates," to lower the tidal regime over one site, effectively reversing sea level rise at a local level. Measured indicators of saltmarsh cover, number of species, seedling counts, and saltmarsh assemblages all showed significant positive development over time, with trends varying based on saltmarsh zone. The saltmarsh, predominantly Sarcocornia quinqueflora, developed from remnant supralittoral (previously high) marsh which remained at 45% cover to achieve over 15% coverage across the cleared habitat after 3 years. Slower development in the low marsh (<5%) compared to other zones contrasts with other saltmarsh restoration studies which may be due to the unique nature of the restoration method or the nature of Australian saltmarsh species which favor higher elevations and drier conditions. The development of saltmarsh at the treatment site was found to track toward that at comparison sites over time, becoming similar to some comparison sites by the studies end. This study highlights the usefulness of the novel restoration method used and of the measured indicators for assessing saltmarsh development. This innovative tidal control method could play an important role in the future of saltmarsh restoration worldwide. [ABSTRACT FROM AUTHOR]

This article examines the adverse effect of rapid industrialization around Bangladesh's Dhaka Export Processing Zone (DEPZ) by analyzing Landsat satellite images captured between 1989 and 2019. Image classification was performed to separate built-up areas with machine learning algorithms in Google Earth Engine. Image analysis was conducted using ArcMap and ArcGIS Pro. Field observations, interviews, and the literature review provided information for explanations about the phenomenon observed from satellite image analyses. The findings reveal that when DEPZ started its operation in 1993, there was hardly any built-up area in the vicinity. Within three decades, over 25% of the land within a 5 km radius of DEPZ has been converted into a built-up area, triggering an almost seven-fold increase in population. Industrial and urban growth in the DEPZ area has caused significant soil and water pollution in the broader region. As a result, the quantity and quality of agricultural land has degraded. In the long run, the planned industrial development initiative has contributed to unsustainable urban growth and environmental consequences. Insights drawn from this article can guide policymakers to re-evaluate their policy for rapid and large-scale industrialization. [ABSTRACT FROM AUTHOR]

Despite the global distribution of sawsharks, little is known about their diets or their role in the marine biosphere. As species in higher trophic positions are generally considered to be more at risk to perturbations such as fishing, understanding their role in the food chain will enable better conservation and management strategies for these species. Two sawshark species (Pristiophorus cirratus, Pristiophorus nudipinnis) co-occur in waters off east Tasmania, Australia. This study determined the trophic positions of these sawsharks and whether they avoided competing with each other through resource partitioning. Isotopic analysis of muscle tissue revealed that P. cirratus and P. nudipinnis had significantly different trophic levels, with P. cirratus likely to have a diet of primary consumers and P. nudipinnis likely to have a piscivorous diet. Owing to their different isotopic signatures, it is also likely that the sawshark rostrum has multiple functions. Both species shifted to higher trophic levels during ontogeny. Maternal isotopic signatures were detectable in P. cirratus juveniles. Malgre la repartition planetaire des requins-scies, leurs regimes alimentaires et le role qu'ils jouent dans la biosphere marine demeurent meconnus. Comme les especes de position trophique superieure sont generalement considerees comme etant plus vulnerables aux perturbations comme la peche, la comprehension de leur role dans la chaine alimentaire permettra d'ameliorer les strategies de conservation et de gestion visant ces especes. Deux especes de requins-scies (Pristiophorus cirratus, Pristiophorus nudipinnis) coexistent dans les eaux au large de la Tasmanie orientale (Australie). L'etude a permis de determiner les positions trophiques de ces requins-scies et d'etablir s'ils evitaient de se faire concurrence grce au partage differentiel des ressources. L'analyse isotopique de tissus musculaires a revele que P. cirratus et P. nudipinnis occupent des niveaux trophiques significativement differents, P. cirratus etant susceptibles d'avoir un regime alimentaire constitue de consommateurs primaires et P. nudipinnis etant susceptible d'avoir une alimentation piscivore. Etant donne ces signatures isotopiques distinctes, il est egalement probable que les rostres des requins-scies aient plus d'une fonction. Les deux especes passaient a des niveaux trophiques plus eleves durant l'ontogenese. Des signatures isotopiques maternelles etaient decelables chez les P. cirratus juveniles. [Traduit par la Redaction], Introduction Species living in close proximity will tend to reduce competition through niche divergence or resource partitioning when faced with limited resources (Ross 1986; Schoener 1974). While terrestrial animals generally [...]