Walk Free Foundation

Abstract Marine heatwaves, and other extreme climatic events, are driving mass mortality of habitat‐forming species and substantial ecological change worldwide. However, habitat fragmentation is rarely considered despite its role in structuring seascapes and potential to exacerbate the negative impacts of habitat loss. Here, we quantify fragmentation of globally significant seagrass meadows within the Shark Bay World Heritage Area before and after an unprecedented marine heatwave impacting the Western Australian coastline over the austral summer of 2010/11. We use a spatial pattern index to quantify seagrass fragmentation from satellite‐derived habitat maps (2002, 2010, 2014 and 2016), assess potential predictors of fragmentation and investigate seascape dynamics defined by relationships between seagrass fragmentation and cover change. Our spatiotemporal analysis illustrates widespread fragmentation of seagrass following the marine heatwave, contributing to a dramatic alteration of seascape structure across the World Heritage Area. Fragmentation immediately following the marine heatwave coincided with widespread seagrass loss and was best explained by interactions between a heat stress metric (i.e. degree heating weeks) and depth. Based on the relationship between fragmentation and seagrass cover change, we revealed near‐ubiquitous fragmentation from 2014 to 2016 represents a mixture of long‐term seagrass degradation and evidence of early, patchy recovery. Fragmentation effects are expected to compound the ecological impacts of seagrass mortality following the marine heatwave and prolong recovery. As sea temperatures and the threat of marine heatwaves continue to rise globally, our results highlight the importance of considering fragmentation effects alongside the negative impacts of habitat loss. Our seascape dynamic framework provides a novel approach to define the response of habitat‐forming species to disturbances, including marine heatwaves, that integrates the processes of fragmentation and cover change. This framework provides the opportunity to consider these important processes across a range of threatened ecosystems and identify areas of vulnerability, stability and recovery.

We present Ocean Genomes, a program dedicated to producing reference genome resources to facilitate improved monitoring approaches and management outcomes for marine vertebrate biodiversity. Ocean Genomes will generate high-quality reference genomes of representatives of all marine vertebrate families and additional high-conservation-value species. Draft-quality genomes may be produced for a more comprehensive sampling of species. We include case studies of Enoplosus armatus, Old Wife and Pempheris klunzingeri, Rough Bullseye.

Abstract Scleractinian reproductive biology has been a focus of research since the discovery of multi-species synchronous spawning in the early 1980s; however, predicting when colonies will spawn on the Great Barrier Reef remains problematic. Here, we combine over 30 years of direct coral spawning observations that include colonies from 128 species from 44 genera in 10 families with 20 years of data on the stage of gamete maturity in colonies of Acropora (hereafter, colony reproductive condition) from the Palm Island group on the Great Barrier Reef to explore patterns within and among species. We find the lunar month counted from the southern hemisphere winter solstice better predicts the first month of spawning in the Palm Islands than the Gregorian month: spawning was never observed before the 5th lunar month. Direct observations suggest that most coral spawning in the Palm Islands occurs in the 5th and 6th lunar months over a 12-day interval starting one day before the full moon, between 30 min before and 5 h after sunset. Split spawning was also a frequent occurrence in Acropora populations. Some Acropora spp. had colonies that spawned in four or five different lunar months, a pattern that might be affected by taxonomic uncertainty. The range in spawning start times was considerably greater among colonies maintained in the laboratory vs those in the field, suggesting that spawning times are affected by handling. This work highlights the importance of a systematic approach to documenting spawning times to improve our understanding of spawning synchrony and seasonality.

ABSTRACTGlobal responses to climate change vary across ecosystems. Identifying coral reefs that can persist despite extreme warming is crucial for guiding research, policy, and management. Resilience frameworks recommend protecting potential reef sanctuaries with specific attributes, including climate avoidance, rapid recovery, or resistance. However, climate‐avoidant reefs are dwindling, and recovery times are lengthening. We propose that resistance should be the cornerstone of reef resilience planning. A literature synthesis reveals that the definition and application of “reef resistance” are highly variable, limiting its effectiveness in management and policy. Over 85% of sources suggest that evolutionary processes contribute to resistance, but there is considerable variability in other cited ecological factors. We highlight a mismatch between implied mechanisms and actual data, with only ∼25% of studies linking resistance to relevant coral adaptation or acclimatization data. To address this, we propose a standardized definition of heat‐resistant reefs based on adaptation and acclimatization principles: reefs characterized by corals whose underlying genetics enable survival beyond previous thermal limits. This approach will enhance the effective allocation of limited resources for measuring, protecting, and managing reefs, as we strive to halt the human‐induced emissions driving their decline.

ABSTRACT Aim For free‐living Symbiodiniaceae, we aim to synthesise current knowledge, identify gaps in our understanding of biogeography and conduct the first quantitative genetic analysis of biogeography at a global scale. Location Global. Taxon Free‐living dinoflagellates of the Family Symbiodiniaceae. Methods Publicly available sequences were used to characterise the free‐living Symbiodiniaceae community in the environment. Using the genetic ITS2 marker combined with the DADA2 pipeline, amplicon sequence variants (ASVs) were used to assess Symbiodiniaceae diversity, abundance and distribution patterns from local to global scales. Results Relative abundances, community composition and sequence diversity differed significantly between the wider Caribbean and Indo‐Pacific, within the Indo‐Pacific, and across our three study regions: Great Barrier Reef (GBR), Flower Garden Banks National Marine Sanctuary (FGBNMS) and Moorea in French Polynesia. Symbiodiniaceae community assemblage was most different between the GBR and FGBNMS, with a dominance of Cladocopium in the GBR and Breviolum in FGBNMS. There was also significant variability within these regions, as shown through a beta dispersion test. The highest diversity indices were found in the GBR, followed by Moorea and FGBNMS. Main Conclusions We found free‐living Symbiodiniaceae biogeography differed significantly between and within locations at the global scale. Importantly, these global patterns in diversity mirrored local‐scale patterns. These free‐living biogeographical patterns also followed in hospite symbiont community patterns. With most studies of free‐living diversity from the Indo‐Pacific, we highlight the need for expanded sampling efforts in unexplored regions such as the Indian Ocean. Given the potentially significant role of free‐living Symbiodiniaceae in coral acclimation to climate change, identifying and protecting these taxa should be a conservation priority.

Micro and nanosized plastics (MNPs), and a range of associated additive chemicals, have become pervasive contaminants that humans and the environment are exposed to everyday. However, one of the principal challenges in their analysis is adequate strategies to minimise background contamination. Here a blueprint for a specialised plastics and additive-minimised clean room laboratory built for this purpose is presented. Common laboratory construction materials (n = 23) were tested, including acoustic baffles, ceiling materials, floor materials, glazing rubber, and silicone sealant. The % polymer content ranged from 2–76% w/w while the sum concentration of six phthalates ranged from 0.81 (0.73–0.86) to 21000 (15000–27000) mg/kg, assigning many of these materials as inappropriate for use in a clean room environment. The final design of the laboratory consisted of three interconnected rooms, operated under positive pressure with the inner rooms constructed almost entirely of stainless steel. Background concentrations of MNPs and phthalates in the new laboratory were compared to two Physical Containment Level 2 (PC2) laboratory environments, with concentrations of MNPs reduced by > 100 times and phthalates reduced by up to 120 times. This study reports the first known clean room of its kind and provides a blueprint for reference and use by future plastics research.

Global climate change is threatening the persistence of coral reefs as associated summer heatwaves trigger the loss of microalgal endosymbionts (Symbiodiniaceae) from the coral tissues, or coral bleaching. We infected aposymbiotic juveniles of the coral Acropora tenuis with either wildtype (WT10) or heat-evolved (SS1 or SS8) Symbiodiniaceae strains Cladocopium proliferum (formerly referred to as Cladocopium goreaui and Cladocopium C1acro). After 10 months at 27 °C, SS8-juveniles were 2 × larger than SS1- or WT10-juveniles. In response to a simulated heatwave (31 °C for 41 days), the WT10-juveniles bleached and showed a decline in respiration while cell densities and respiration in both SS-juvenile groups remained unchanged compared to the controls. These results reveal that some heat-evolved strains can increase the bleaching tolerance of juvenile corals without a trade-off against growth. This response is opposite to the lower nutrient provisioning often reported for naturally thermotolerant Symbiodiniaceae (e.g. genus Durusdinium), thereby offering enhanced fitness to the host without the ecological consequences of diminished growth.