Further Flattening of a Degraded, Turbid Reef System Following a Severe Coral Bleaching Event

Increasing incidence of severe coral bleaching events caused by climate change is contributing to extensive coral losses, shifts in species composition and widespread declines in the physical structure of coral reef ecosystems. With these ongoing changes to coral communities and the concomitant flattening of reef structural complexity, understanding the links between coral composition and structural complexity in maintaining ecosystem functions and processes is of critical importance. Here, we document the impacts of the 2016 global-scale coral bleaching event on seven coral reefs in Singapore; a heavily degraded, turbid reef system. Using a combination of field-based surveys, we examined changes in coral cover, composition and structural complexity before, during and after the 2016 bleaching event. We also quantified differential bleaching responses and mortality among coral taxa and growth forms using a bleaching response index. Elevated SSTs induced moderate to severe coral bleaching across reefs in Singapore in July 2016, but low overall coral mortality (~12% of colonies). However, we observed high bleaching prevalence and post-bleaching mortality of the three most abundant coral genera (Merulina, Pachyseris and Pectinia), all generalists, declined significantly across reefs between March and November 2016. Four months post-bleaching (November 2016), small-scale structural complexity declined across all Singaporean reefs and no moderately complex reefs remained. Importantly, reductions in structural complexity occurred across reefs with a large range of live coral cover (19–62%) and was linked to the loss of dominant coral genera with low-profile foliose-laminar growth forms which resulted in flatter, less structurally complex reefs. And while generalist coral taxa remain highly competitive within Singapore’s reef environment, they may not have the capacity to maintain structural complexity or ensure the persistence of other reef functions, even within communities with high coral cover. The widespread loss of structurally complexity on Singapore’s degraded coral reefs may further impair ecosystem functioning, potentially compromising the long-term stability of reef biodiversity and productivity

Accreting coral reefs in a highly urbanized environment

Globally, many coral reefs have fallen into negative carbonate budget states, where biological erosion exceeds carbonate production. The compounding effects of urbanization and climate change have caused reductions in coral cover and shifts in community composition that may limit the ability of reefs to maintain rates of vertical accretion in line with rising sea levels. Here we report on coral reef carbonate budget surveys across seven coral reefs in Singapore, which persist under chronic turbidity and in highly disturbed environmental conditions, with less than 20% light penetration to 2 m depth. Results show that mean net carbonate budgets across Singapore’s reefs were relatively low, at 0.63 ± 0.27 kg CaCO3 m−2 yr−1 (mean ± 1 SE) with a range from − 1.56 to 1.97, compared with the mean carbonate budgets across the Indo-Pacific of 1.4 ± 0.15 kg CaCO3 m−2 yr−1, and isolated Indian Ocean reefs pre-2016 bleaching (~ 3.7 kg CaCO3 m−2 yr−1). Of the seven reefs surveyed, only one reef had a net negative, or erosional budget, due to near total loss of coral cover (\u3c 5% remaining coral). Mean gross carbonate production on Singapore’s reefs was dominated by stress-tolerant and generalist species, with low-profile morphologies, and was ~ 3 kg m−2 yr−1 lower than on reefs with equivalent coral cover elsewhere in the Indo-Pacific. While overall these reefs are maintaining and adding carbonate structure, their mean vertical accretion potential is below both current rates of sea level rise (1993–2010), and future predictions under RCP 4.5 and RCP 8.5 scenarios. This is likely to result in an increase of 0.2–0.6 m of water above Singapore’s reefs in the next 80 yr, further narrowing the depth range over which these reefs can persist

Growth and carbonate production of crustose coralline algae on a degraded turbid reef system

Crustose coralline algae (CCA) and other encrusting calcifiers drive carbonate production on coral reefs. However, little is known about the rates of growth and calcification of these organisms within degraded turbid reef systems. Here we deployed settlement cards (N = 764) across seven reefs in Singapore for two years to examine spatio-temporal variation in encrusting community composition and CCA carbonate production. Our results showed that CCA was the dominant encrusting taxa (63.7% ± 18.3SD) across reefs. CCA carbonate production rates (0.009–0.052 g cm−2 yr−1) were less than half of those reported for most Indo-Pacific reefs, but similar to other turbid reef systems. Highest CCA carbonate production rates were observed furthest from Singapore\u27s main shipping port, due to a relative increase in CCA cover on the offshore reefs. Our results suggest that proximity to areas of high industrialisation and ship traffic may reduce the cover of encrusting calcifying organisms and CCA production rates which may have negative, long-term implications for the stabilisation of nearshore reefs in urbanised settings

Fear effects associated with predator presence and habitat structure interact to alter herbivory on coral reefs

Foraging decisions made by consumers are driven by a range of factors, including non-consumptive predation effects. These effects are often mediated by both the presence or absence of predators, and the structure of the surrounding habitat that may visually occlude prey, thus increasing the predation risk. Under such circumstances, it is likely that prey will be warier, and this will be reflected in their rates of browsing. We used models of the predatory coral reef fish Plectropomus leopardus and experimentally manipulated the density of the macroalga Sargassum ilicifolium to investigate how these factors interact on a coral reef in Singapore. We found that the interaction between predator- and habitat associated fear effects influence the rate of herbivory, with declining rates with increasing macroalgal density, likely due to visual occlusion by macroalgae making it more difficult to detect predators, and thus increasing wariness in browsers. The predator model appeared to have an impact on browsing, but only at low-densities of Sargassum. Our results suggest that when fishes' knowledge of their surroundings is less certain, they will respond with a heightened wariness, regardless of acute predation cues

‘Bunkering down’: How one community is tightening social-ecological network structures in the face of global change

Complex networks of relationships among and between people and nature (social-ecological networks) play an important role in sustainability; yet, we have limited empirical understanding of their temporal dynamics. We empirically examine the evolution of a social-ecological network in a common-pool resource system faced with escalating social and environmental change over the past two decades. We first draw on quantitative and qualitative data collected between 2002 and 2018 in a Papua New Guinean reef fishing community to provide contextual evidence regarding the extent of social and environmental change being experienced. We then develop a temporal multilevel exponential random graph model using complete social-ecological network data, collected in 2016 and 2018, to test key hypotheses regarding how fishing households have adapted their social ties in this context of change given their relationships with reef resources (i.e. social-ecological ties). Specifically, we hypothesized that households will increasingly form tight-knit, bonding social and social-ecological network structures (H1 and H3, respectively) with similar others (H2), and that they will seek out resourceful actors with specialized knowledge that can promote learning and spur innovation (H4). Our results depict a community that is largely ‘bunkering down’ and looking inward in response to mounting risk to resource-dependent livelihoods and a breakdown in the collaborative processes that traditionally sustained them. Community members are increasingly choosing to interact with others more like themselves (H2), with friends of friends (H1), and with those connected to interdependent ecological resources (H3)—in other words, they are showing a strong, increasing preference for forming bonding social-ecological network structures and interacting with like-minded, similar others. We did not find strong support for H4. Bonding network structures may decrease the risk associated with unmonitored behaviour and help to build trust, thereby increasing the probability of sustaining cooperation over time. Yet, increasing homophily and bonding ties can stifle innovation, reducing the ability to adapt to changing conditions. It can also lead to clustering, creating fault lines in the network, which can negatively impact the community\u27s ability to mobilize and agree on/enforce social norms, which are key for managing common resources

A global review of marine recreational spearfishing

24 pages, 5 figures, 2 tables, supplementary information https://doi.org/10.1007/s11160-023-09790-7.-- Data availability: The full list of papers used for the systematic review is available as a supplementary tableRecreational spearfishing is a fishing method that occurs globally, yet receives considerably less attention in the scientific literature relative to other recreational fishing methods, such as angling. Lack of scientific information on spearfishing may negatively affect the development and management of marine recreational fisheries. We conducted a systematic review of 102 peer-reviewed papers published between 1967 and 2022 pertaining to marine recreational spearfishing. Based on this literature review, we provide an overview of key insights across social, economic, and ecological dimensions of marine recreational spearfishing. While spearfishers represent less than 5% of marine recreational fishers, the participants are younger and may differ from recreational anglers in their motivations, with suggestions of increased well-being generated from a close connection with the sea during underwater fishing. Recreational spearfishers mostly target species of moderate to high levels of vulnerability that are mid to high trophic level carnivores. Though spearfishers can deliberately target larger individuals of exploited populations, this is not a generalizable pattern. Despite a growing body of research on the ecological impacts of marine recreational spearfishing, there is limited knowledge of these effects and their mechanisms across biological levels of organization (e.g., individual, population, community and ecosystem) compared with those of other fishing methods. Recreational spearfishers can contribute to advances in marine ecological knowledge, and inclusive participatory management could represent a key step towards transformative sustainable development of marine recreational spearfishing. Throughout the review, we identify gaps in the research and areas where future research is needed to better inform the socio-economic importance, ecosystem impacts and future management of marine recreational spearfishingVS was supported by a “Juan de la Cierva Incorporación” (IJC2018-035389-I), and he is now supported by a “Ramón y Cajal” research fellowships (RYC2021-033065-I) granted by the Spanish Ministry of Science and Innovation. SV and PP are supported by the Xunta de Galicia (RECREGES I and II projects under Grants ED481B2014/034-0 and ED481B2018/017), Grupo de Referencia Competitiva GI-2060 AEMI, under Grant ED431C2019/11), and Fundación Biodiversidad, Ministerio para la Transición Ecológica y el Reto Demográfico, Gobierno de España (SICORE and GT PMR projects). VJG received a postdoctoral grant (#2017/22273-0) from São Paulo Research Foundation (FAPESP). MR would like to acknowledge Portuguese national funds from FCT—Foundation for Science and Technology through projects UIDB/04326/2020, UIDP/04326/2020 and LA/P/0101/2020. MR would also like to acknowledge FCT funding through a postdoctoral grant (SFRH/BPD/116307/2016). JACCN thanks to Meros do Brasil Project sponsored by Petrobras. FJH is supported by a Sȇr Cymru European Regional Development Fund Fellowship (80761-SU-135). RA was supported by the German Federal Ministry of Education and Research (Grants 01LC1826E and 033W046A). ML is supported by the Agencia Nacional de Investigación e Innovación (ANII, POS_EXT_2020_1_165362). This work acknowledges the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S). [...] Open Access funding provided thanks to the CRUE-CSIC agreement with Springer NaturePeer reviewe

COVID-19 influences on US recreational angler behavior

Recreational angling in the United States (US) is largely a personal hobby that scales up to a multibillion-dollar economic activity. Given dramatic changes to personal decisions and behaviors resulting from the COVID-19 pandemic, we surveyed recreational anglers across the US to understand how the pandemic may have affected their fishing motivations and subsequent activities. Nearly a quarter million anglers from 10 US states were invited to participate in the survey, and almost 18,000 responded. Anglers reported numerous effects of the pandemic, including fishing access restrictions. Despite these barriers, we found that the amount of fishing in the spring of 2020 was significantly greater-by about 0.2 trips per angler-than in non-pandemic springs. Increased fishing is likely associated with our result that most respondents considered recreational angling to be a COVID-19 safe activity. Nearly a third of anglers reported changing their motivation for fishing during the pandemic, with stress relief being more popular during the pandemic than before. Driven partly by the perceived safety of social fishtancing, recreational angling remained a popular activity for many US anglers during spring 2020

Accreting coral reefs in a highly urbanized environment

10.1007/s00338-020-01953-3Coral Reef

‘Bunkering down’: How one community is tightening social-ecological network structures in the face of global change

Complex networks of relationships among and between people and nature (social-ecological networks) play an important role in sustainability; yet, we have limited empirical understanding of their temporal dynamics. We empirically examine the evolution of a social-ecological network in a common-pool resource system faced with escalating social and environmental change over the past two decades. We first draw on quantitative and qualitative data collected between 2002 and 2018 in a Papua New Guinean reef fishing community to provide contextual evidence regarding the extent of social and environmental change being experienced. We then develop a temporal multilevel exponential random graph model using complete social-ecological network data, collected in 2016 and 2018, to test key hypotheses regarding how fishing households have adapted their social ties in this context of change given their relationships with reef resources (i.e. social-ecological ties). Specifically, we hypothesized that households will increasingly form tight-knit, bonding social and social-ecological network structures (H1 and H3, respectively) with similar others (H2), and that they will seek out resourceful actors with specialized knowledge that can promote learning and spur innovation (H4). Our results depict a community that is largely ‘bunkering down’ and looking inward in response to mounting risk to resource-dependent livelihoods and a breakdown in the collaborative processes that traditionally sustained them. Community members are increasingly choosing to interact with others more like themselves (H2), with friends of friends (H1), and with those connected to interdependent ecological resources (H3)—in other words, they are showing a strong, increasing preference for forming bonding social-ecological network structures and interacting with like-minded, similar others. We did not find strong support for H4. Bonding network structures may decrease the risk associated with unmonitored behaviour and help to build trust, thereby increasing the probability of sustaining cooperation over time. Yet, increasing homophily and bonding ties can stifle innovation, reducing the ability to adapt to changing conditions. It can also lead to clustering, creating fault lines in the network, which can negatively impact the community's ability to mobilize and agree on/enforce social norms, which are key for managing common resources.</p

Periodically harvested closures require full protection of vulnerable species and longer closure periods

Periodically harvested closures (PHCs) are small fisheries closures with objectives such as sustaining fisheries and conserving biodiversity and have become one of the most common forms of nearshore marine management in the Western Pacific. Although PHCs can provide both short-term conservation and fisheries benefits, their potential as a long-term management strategy remains unclear. Through empirical assessment of a single harvest event in each of five PHCs, we determined whether targeted fishes that differ in their vulnerability to fishing recovered to pre-harvest conditions (the state prior to last harvest) and demonstrated post-harvest recovery benefits after 1 year of re-closure. For low and moderately vulnerable species, two PHCs provided significant pre-harvest benefits and one provided significant post-harvest recovery benefits, suggesting a contribution to longer-term sustainability. PHCs with a combination of high compliance and longer closing times are more likely to provide fisheries benefits and recover from harvest events, however, no benefits were observed across any PHCs for highly vulnerable species. We recommend PHCs have longer closure periods before being harvested and species that are highly vulnerable to fishing (e.g. large species of; grouper, wrasse and parrotfish) are avoided during harvests to avoid overexploitation and increase the sustainability of small-scale fisheries