Search

Coral reefs are facing a constant barrage of human impacts, including eutrophication, overharvesting and climate change. However, research and management are just beginning to depart from a single-dominant-stressor paradigm and a holistic ecosystem-based understanding of these systems is still in its infancy. We expand on a well-known theoretical model to motivate an integrated multi-stressor framework for coral reefs by incorporating empirical evidence of multi-stressor impacts (overfishing, eutrophication and climate-driven mortality) as well as general ecological and theoretical concepts. We show that: i) the geometry of a simple, empirically-motivated model suggests nutrients and harvesting can operate similarly in driving shifts from coral- to algae-dominated reefs; ii) these impacts increase nonlinearly when acting concurrently, resulting in clear context-dependent management implications; and iii) this same geometry suggests climate-driven coral mortality (temperature-stress, cyclonic storms) can drive the presence of long transients and climate-driven alternate states, even in moderately-impacted ecosystems. These results imply that reefs that appear to be in a “safe space” may in fact be in danger of being pushed into a degraded algae-dominated state as storms and bleaching events are increasing in frequency and magnitude. Altogether, we find that responses in benthic composition as “signatures of change” to multi-stressors allows us to develop a predictive multi-stressor framework for coral reefs. In line with this theory, we detail empirical evidence from Barbados that highlights the context-dependent nature of coral reefs in a changing world. Our results present novel and generalizable insights into the functioning of coral reefs, that draw from classic theoretical and ecological concepts such as keystone predation theory, ecological succession and life history theory, as well as the emerging fields of long transients and early warning signals. By bridging coral reef ecology and general ecological concepts, we can better understand ecosystem functioning and resilience in these important yet highly threatened systems.Open Research Statement: Data used in this manuscript are already published and publicly available. Sources can be found within the manuscript and in Supplement B. Mathematical analyses and simulations were performed in Wolfram Mathematica (version 12.1.0.0); code is available at: https://github.com/carlingbieg/corals

In Belize, the commercial harvest of spiny lobsters has occurred for ∼100 years, provides critical livelihoods, and is the primary seafood export. We determined the first empirical estimate of size at maturity in Belize as well as eight fishery status indicators on several fishing grounds. The carapace lengths (CLs) at 50% maturity varied between males (98 mm) and females (86 mm) and are higher than the existing legal minimum of 76 mm. Time series analysis indicated decreasing proportions of mature individuals, decreasing size, and low spawning potential ratios (SPR) as well as high fishing mortality within fishing grounds. The pattern of decline in population status indicators across fishing grounds is consistent with a historical expansion of effort from north to south and offshore. Many indicators of population status within fishing grounds were improved with increasing area of replenishment zone and opposite to the historical expansion. However, overfishing is a problem across all areas examined. An increase in the legal minimum CL to 86 mm and examination of a maximum size limit will likely have significant positive effects on productivity and SPR, respectively, as well as protecting the pivotal role of spiny lobsters within the ecosystem.

Studies using paleoecological and historical data can inform coral reef management by providing accurate ecological baselines and by pinpointing the timing, magnitude, and drivers of ecosystem declines. However, these studies have rarely been incorporated into policy and management frameworks. This working group brings together paleontologists, historical ecologists, ecologists, fisheries scientists, and conservation practitioners to develop pathways for incorporating long-term ecological data into decision-making to advance the sustainable management of reef ecosystems. Our group is focusing on Caribbean coral reefs, a geography with an abundance of historical ecological data and a track record of collaboration between reef scientists and managers. This spirit of collaboration is enhanced by the immediacy of conservation needs for reef ecosystems in this region. We are focusing on the application of long-term data to two pressing management issues for Caribbean coral reefs, which together address the most urgent local human drivers of ecosystem change – fishing and land-based pollution. In this talk, I will outline our working group’s aims and progress to date.

Caribbean coral reef ecosystems have declined dramatically since systematic monitoring began in the 1970s. Over the past 50 years, they have lost between 50-80% of reef-building corals, their principal ecosystem architects. These declines have been attributed to climate change, introduction of invasive species, overfishing, and land-based pollution. Although recognized as a major stressor to corals, the role of land-based pollution in Caribbean coral declines has not been quantified due to the lack of consistent reef water quality monitoring. As part of our CPN-funded working group “Integrating paleo and historical data into coral reef management and policy”, we compiled several metrics of reef water quality from paleoecological data and disparate monitoring efforts across the Caribbean to document multidecadal-scale change over a period of intensifying coastal land alteration. We then compared water quality trends with trends in living coral cover from these same reefs to assess the role of water quality declines from land-based runoff on coral reef ecosystem health. These analyses show that (1) an array of historical data exist for reconstructing trends in Caribbean reef water quality that are in disparate repositories and remain mostly untapped, (2) reefs across the Caribbean have experienced water quality declines over the past half century, even offshore sites that were previously thought to be unaffected by land-based runoff, (3) correlations between reef water quality and coral abundance trends are detected at select sites where water quality monitoring protocols were consistent and sustained for multiple decades, and (4) water quality declines are asynchronous across sites and are likely related to differing timing and histories of land alteration.

Queen conch (Lobatus gigas) is a large herbivorous gastropod, found across the Caribbean, which forms the basis of important dive fisheries. Conch have a two‐phase shell growth pattern, first in shell length (SL), which ceases well before maturity, followed by growth in shell lip thickness (LT) into maturity. This growth pattern must be considered in determining the ideal size and associated maturity for sustainable harvest. Shell morphology, sex organ development and soft tissue masses indicated that mature adult conchs at Glover's Atoll, Belize, were those with thick shell lips (≥10 mm), eroded shells and heavier soft tissue masses. Therefore, SL‐based regulations cannot serve as a proxy for maturity and harvest. The use of inappropriate minimum size limits (SL = 178 mm, 85 g market clean meat mass) has allowed significant juvenile harvest and the fishery appears to have truncated the SL size distribution of conchs with a flared shell lip (i.e. adults) over the last 15 years. The reduced SL observed in lipped conchs may lead to a significant impact on the reproductive success of the population as well as diminished economic yield from the fishery, as smaller adult conchs of the same age have lower gonad and meat weight. We believe this to be the first documentation of a decline in the SL of adult queen conchs, and that the SL‐based size limits have contributed to this decline. Refinement of the individual size‐based regulations for conch in Belize to LT will probably facilitate local recovery as well as regional harmonization of regulations. Future research in Belize should include movement dynamics of conch in relation to replenishment zone size and spillover as well as the importance of deep‐water conch to shallow‐water recruitment, which is thought to be limited.

Using information on the species composition and length-frequencies of fish caught in the spear and hook and line fisheries of Glover’s Reef Marine Reserve, Belize, we evaluated changes between 2004–2010 and 2011–2017 in single-species and ecosystem sustainability indicators. The two gears differed in species caught, and both changed species composition between time periods, with the line fishers targeting smaller species, and the spear fishers responding to a parrotfish ban by catching more snappers and small groupers, as well as grey angels. Both gears caught smaller fish in 2011–2017 compared to 2004–2010, indicating overfishing. Species often caught immature were black grouper, Nassau grouper and mutton snapper with spears, and black snapper with lines. Most fish of other species were mature, but many were smaller than the optimal size for harvest. Fishing mortality rates were higher than natural mortality rates for most species in both gears in both time periods, whether calculated from average length or by length-based spawning potential ratio (LBSPR), implying that most populations were experiencing overfishing. Many species also had a low spawning potential ratio, implying a high probability that they were overfished. In general, many species were subject to unsustainable levels of fishing, and, according to the Froese indicators, some would benefit from size limits to protect immature individuals. These results are supported despite uncertainty in life history parameters for fishes in Belize, and differences between data poor assessment methods.

Macroalgal blooms are increasing on the Belize Barrier Reef (BBR) as scleractinian coral cover declines. Although some have attributed this to reduced grazing, the role of land-based nutrient pollution has not been assessed. Nutrient enrichment was quantified through macroalgal tissue analysis from Belize City to the offshore fore reef and at several central BBR lagoon sites. These recent data were compared to baseline data from the 1980s. Significant nearshore-to-offshore gradients of %N, %P and δ13C in macroalgae all indicated land-based sources of these nutrients. Macroalgal δ15N values were generally enriched in nearshore waters where values matched those reported for human sewage. Notably, the N:P ratios of recent macroalgae measurements were elevated at all sites, more than two-fold higher than values from the 1980s (~30: 1 to 70:1). These results support the hypothesis that nitrogen enrichment from land-based sources has increased phosphorus limitation driving macroalgal blooms and coral stress on the BBR.

In the face of climate change, warming oceans, and repeated mass coral bleaching, coral reef conservation is at a timely crossroads. There is a new urgency to support and strengthen a rich history of conservation partnerships and actions, while also building toward new actions to meet unparalleled global threats. The goal of this white paper is to synthesize and summarize the diversity of tools, approaches and solutions for coral reef conservation implemented to date and to understand the enabling conditions that lead to successful coral reef conservation. Framed as a “solution-scape,” this white paper seeks to support ongoing decisions to strengthen existing assets and build new investments into portfolios of global coral reef conservation that are equitable and aligned with diverse cultures and worldviews. We conclude with 10 recommendations that focus on equitable conservation practices that will align successful interventions with diverse cultures and worldviews, help ensure that the right decisions are made, and strengthen investments into conservation portfolios that will lead to successful coral reef conservation.

Unsustainable wildlife trade negatively impacts wild populations of traded species. Thus to assess these population impacts and manage trade, we need to find and characterize extant populations. Seahorses are one of the most heavily traded marine animals, with almost 6 million individuals exported worldwide annually. Thailand, the top exporter, is responsible for 88% of global export volumes of dried seahorses. Here, we sought to locate seahorse hotspots in Thailand - places where seahorses are still abundant, and elucidate predictors of these hotspots. Because seahorses have economic value, we included socio-economic parameters in addition to environmental parameters. From underwater surveys, 46 seahorses from three species were spotted at 13 of 46 sites, with Hippocampus spinosissimus most commonly observed. The highest seahorse densities were found off Chonburi province within the Gulf of Thailand. Seahorse density and presence were not significantly associated with habitat type, while access to market was the strongest predictor. Seahorses were less abundant in areas with a seahorse market, presumably because proximate seahorse resources in these areas are attractive commodities to extract for fishers. Intense fishing activity has already greatly impacted seahorse populations in Thailand, potentially obscuring natural habitat preferences and leading to population declines. For heavily traded species whose natural populations are already impacted, human processes may have a stronger effect on species distribution than habitat type or quality. Beyond identifying and protecting suitable habitats, the preservation of seahorse populations depends on changing human behavior in interacting with seahorses and the strict enforcement of existing fishing regulations.

This paper describes the application of the methodology called Rapid Appraisal of Fisheries Management System (RAFMS) to assess quickly the situation in tsunami-affected coastal fisheries in Aceh Province, Indonesia. As a diagnostic tool, the RAFMS is introduced in terms of its conceptual framework and procedures. The RAFMS was used to appraise the status of the fisheries sector in selected 15 villages. Information generated concerning level of fishing effort, marketing patterns and community perspectives on livelihood options are used as three illustrative examples. The paper also provides some insights in applying the RAFMS methodology in the context of disasters and in the broader context of tropical fisheries management.

Restoration has become an integral part of coastal management as a result of seagrass habitat loss. We studied restoration of the seagrass (Halodule wrightii) near Tampa Bay, Florida. Experimental plots were established in June 2002 using four planting methods: three manually planted and one mechanically transplanted by boat. Seagrass cover was recorded at high resolution (meter scale) annually through July 2005. Natural seagrass beds were concurrently examined as reference sites. We also evaluated the suitability of a commonly used protocol (Braun-Blanquet scores, BB) for comparing the development of seagrass cover using the planting methods and quantifying spatial patterns of cover over time. Results show that BB scores mirrored conventional measures of seagrass characteristics (i.e., shoot counts and above- and belowground biomass) well when BB scores were either low or very high. However, more caution may be required at intermediate cover scores as judged by comparison of BB scores with direct measurement of seagrass abundance. Significant differences in seagrass cover were detected among planting methods and over time (2002–2005), with manual planting of rubber band units resulting in the highest cover. In contrast, the peat pot and mechanical planting methods developed very low cover. Recovery rates calculated from development of seagrass spatial cover were less than those reported for natural expansion. Importantly, time to baseline recovery may be substantially greater than 3 years and beyond standard monitoring timelines. Prolonged recovery suggests that the rate of service returns, critical for estimating compensatory restoration goals under habitat equivalency analysis, may be severely underestimated.

Anthropogenic nutrient enrichment has resulted in significant changes in food web structure. Although such changes have been associated with the loss of diversity and ecosystem services, little empirical work has been done to study food webs of similar systems across a nutrient enrichment gradient. We examined 11 seagrass beds along a gradient of increasing δ15N of primary consumers, where δ15N is used as an indicator of sewage-derived nutrients. Observations across this gradient revealed corresponding increases in consumer density and changes in distinct functional groups, whereas consumer diversity, seagrass canopy, and macrodetrital biomass decreased. However, maximum overall primary consumer diversity and minimum density occurred at intermediate levels along the nutrient gradient. We hypothesize that higher species diversity at low to moderate levels of nutrient enrichment depends on the persistence of grazer-resistant seagrass. This seagrass canopy, and the significant macrodetritus it generates, facilitates a variety of food and shelter resources. Overgrazed and simplified habitats may occur when densities of generalist urchins, capable of direct producer consumption, are no longer controlled through competition, predation, and intraguild predation. We hypothesize that high and stable urchin populations appear possible with the increased availability of allochthonous phytoplankton and associated particulate detritus that is a well-known consequence of nutrient enrichment in aquatic systems.

Although the roles of physical disturbance and successional recovery from such distur-bances in structuring natural communities are well known, recent studies have begun to uncover thepotential for alternate outcomes or climax states in a number of systems. Here, we examine the dis-tribution of tropical macrophytes at a site with heavy wave exposure and explore equilibrium (micro-habitat) and non-equilibrium (patch-dynamic) hypotheses to explain the observed pattern. The exis-tence of a large and distinct zone of prolific macroalgae, undescribed 30 yr earlier, situated between2 zones with a relatively high abundance of seagrass, challenges the classic successional regimewithin Caribbean macrophyte beds. Significantly smaller mean size and lower frequency of acutedisturbances within the macroalgal-dominated zone, as compared to the outer, mixed macrophytezone, appears to contradict the highly disturbed environment of classic colonizers. The dominance ofmacroalgae in the mid-shore zone may be enhanced by the presence of large sediment sizes that areaccumulated through the effect of chronic wave stress. Potential causes of overall changes in thehydrodynamic forces at the study site include rise in sea level, increased wave exposure and associ-ated erosion of reefs protecting the coast. We propose a model of macrophyte bed development anddistribution that includes the important chronic ‘stress’ category of wave energy and potential domi-nance by macroalgae. Increased average wave energy can impose an elevated level of stress leadingto modified patterns of macrophyte distributions and changes in the deterministic endpoint of thesuccessional sequence. KEY WORDS: Succession · Colonization · Competition · Waves · Stress · Gaps · Seagrass ·Macroalgae

The identification and understanding of shifts in resource availability and community structure caused by a variety of anthropogenic perturbations is essential to future rehabilitation efforts and recovery of essential ecosystem processes. We focus here on the contribution of nutrient enrichment to the overgrazing of macrophyte-dominated systems, which has often been linked to predator and competition release of urchins due to overfishing. However, the contribution of nutrient loading to the progression and per- sistence of this phenomenon should also be considered. In an effort to understand the contribution of nutrient loading to the overgrazing phenomenon and associated simplified community in a Caribbean seagrass bed, a detailed isotopic (d 13 C, d 15 N) assessment of the food web structure was conducted at both a nutrient-enriched and a control site. The general pattern at the enriched site indicated significantly lighter d 13 C signatures (i.e., phytoplankton influenced) for non-generalist primary consumers (i.e., specialist grazers, subsurface deposit feeders) and for the sediment organic material (SOM) when compared to the control site. The contribution of phytoplankton and associated particulate organic material to the SOM was also different, 7% vs. 44% at the enriched and control site, respectively. The loss of the autochthonous seagrass detritus pool, in the wake of high densities of generalist urchins (.66 000 individuals/ha) and low overall consumer diversity, appears to have been partially replaced by opportunistic ''alternatives,'' epiphytes but mainly phytoplankton, that benefit directly from elevated input of anthropogenic, allochthonous nutrients. The availability of such alternative, allochthonous resources to generalist urchins could potentially allow for the persistence of simplified seagrass communities. Here, elevated densities of urchins enable a persistent suppression of autochthonous benthic-macrophyte production through grazing and the consumption of newly recruited competitors and predators.

We illustrate the skewed spatial and temporal patterns of fishing effort and the associated non-compliance with regulations within the spiny lobster fishery based in South Caicos, Turks and Caicos Islands. The size, maturity, and breeding status of lobsters caught by divers (4321 from 179 boat trips) from five fishing grounds over the 8-month fishing season correspond well to habitats and depths associated with known life-history stages. More importantly, 63% of lobsters landed during the first month of the season (“The Big Grab”) are immature and 43% are undersized individuals captured in shallow habitats where divers concentrate their efforts. Non-compliance with regulations is not limited to this period with 33% of all lobsters landed being undersized and 10.9% being females in breeding condition (prohibited). It is postulated that this pattern of fishing must have detrimental effects on the population and may partially explain the 66% decline in CPUE observed over the last decade and the 15% decline in mean individual weight of lobster caught over the last 25 years. Several management modifications are suggested that may reduce the skewness in effort and pervasive non-compliance. The importance and utility of collecting fisheries data on discrete and appropriately sized spatial and temporal scales is highlighted.

This study provides a first evaluation of the biological impact of a marine fishery reserve on the stock of queen conch (Strombus gigas) in the Turks and Caicos Islands. The density and the shell length of the population living in the reserve are compared with those of the individuals living in the surrounding fished areas. The results show that the adult density is six times higher in the reserve than in the fished areas. The shell length analysis shows that both adults and juveniles are significantly smaller in the reserve than in the fished area. This unexpected result suggests the existence of a crowding effect (i. e. a high density-induced reduction in growth rate) within the ­reserve. It is hypothesised that this crowding effect is due to the superimposition of two factors leading to very high density values in the reserve: (a) the reduced fishing mortality following the creation of the reserve, (b) the existence of natural barriers that impede the emigration of adults outside the reserve. These results are then discussed in relation to current considerations on marine fisheries reserves.

1. The movement of organisms and dispersal of propagules is fundamental to the maintenance of populations over time. However, the existence of barriers, created through the spatial configuration of habitats, may significantly affect dispersal patterns and thus influence community dynamics and resource sustainability. 2. Within marine environments unstructured or open habitats may form partial or complete ecological barriers due to elevated risk of predation or physical stresses associated with them. The existence and effects of such barriers may be of particular importance when considering the establishment of marine protected areas with a fisheries enhancement focus. 3. In this paper, the spillover of post-settlement queen conch (Strombus gigas) from a protected area in the Turks and Caicos Islands is investigated. It is hypothesized that the reserve boundaries overlap with a series of shallow, sand habitats that effectively enclose the protected population, reducing the spillover of conch into the adjacent fished areas. 4. To test this, density gradient maps for juvenile and adult conch populations were constructed using underwater visual survey data at 68 sites within and surrounding the protected area. These maps illustrate very low densities coinciding with poor, shallow sand habitats along the two marine boundaries of the reserve where spillover is expected to take place. 5. These sand habitats are thought to create ecological barriers to a slow, sedentary gastropod largely due to their shallowness (physical stresses of solar exposure or anoxia) and lack of food reducing the tendency of individuals to move across these areas, despite the 10-times higher density of adult queen conch observed in the protected area compared with outside. Copyright © 2003 John Wiley & Sons, Ltd.

In this paper we analyze the fishing effort allocation of fishermen in the artisanal fisheries of the Turks and Caicos Islands (British West Indies). These fishermen use a free-diving technique to simultaneously exploit the local stocks of queen conch and spiny lobster. Using an integrated framework combining a set of analytical tools within a multi-disciplinary holistic approach, we attempt to identify the biological, economic, and social mechanisms which govern the fishermen's effort allocation between the two targeted stocks. The analysis shows that the seasonal dynamics of the whole system are essentially dictated by the very remunerative lobster fishery. Although this result tends to espouse the predictions of classical economic theory, a closer analysis reveals that the economic rationality approach does not entirely explain the observed fishermen behavior. Information from a series of socio-anthropological surveys shows that the fishermen's decision making is further influenced by collective and individual constraints related to the specific diving abilities required to operate in the two fisheries and by the socio-historico-cultural environment within which the fishing community has been evolving over the last century.

Empirical patterns that emerge from an examination of food webs over gradients of environmental variation can help to predict the implications of anthropogenic disturbance on ecosystems. This "dynamic food web approach" is rarely applied at the coastal margin where aquatic and terrestrial systems are coupled and human development activities are often concentrated. We propose a simple model of ghost crab (Ocypode quadrata) feeding that predicts changing dominant prey (Emerita talpoida, Talorchestia sp., Donax variablis) along a gradient of beach morphology and test this model using a suite of 16 beaches along the Florida, USA coast. Assessment of beaches included quantification of morphological features (width, sediments, slope), macrophyte wrack, macro-invertebrate prey and active ghost crab burrows. Stable isotope analysis of carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) and the SIAR mixing model were used to determine dietary composition of ghost crabs at each beach. The variation in habitat conditions displayed with increasing beach width was accompanied by quantifiable shifts in ghost crab diet and trophic position. Patterns of ghost crab diet were consistent with differences recorded across the beach width gradient with respect to the availability of preferred micro-habitats of principal macro-invertebrate prey. Values obtained for trophic position also suggests that the generalist ghost crab assembles and augments its diet in fundamentally different ways as habitat morphology varies across a highly dynamic ecosystem. Our results offer support for a functional response in the trophic architecture of a common food web compartment (ghost crabs, macro-invertebrate prey) across well-known beach morphologies. More importantly, our "dynamic food web approach" serves as a basis for evaluating how globally wide-spread sandy beach ecosystems should respond to a variety of anthropogenic impacts including beach grooming, beach re-nourishment, introduction of non-native or feral predators and human traffic on beaches.