Global warming is heating the Antarctic circumpolar deep water (CDW), which comes into direct contact with the diverse and abundant macrobenthic communities thriving on the continental shelf of the Weddell Sea (WS). A set of 16 current meters deployed along more than 3000 km coastline revealed that tidal currents drive CDW intrusions onto the WS continental shelf and they can increase the temperature near the seabed by ~2.7 °C. The ongoing ocean warming trend may expose macrobenthic assemblages to ambient temperatures >2 °C by the end of the century with dramatic consequences for communities which have evolved during millions of years in near geophysical isolation under rather constant environmental conditions with temperatures <0 °C. These stenothermal communities have long generation times (therefore, reduced opportunity to mutate) and require hundreds of years for adaptation.
Results from 135 benthic stations along the study area showed that macrobenthic communities in the southeastern section of the WS are the most vulnerable to the increase of temperature near the seabed given their high component of sessile organisms. Besides a dramatic marine biodiversity loss, the eventual demise of these communities, which provide habitat structure for a large number of species that can build up >87 g C m−2, will cause the liberation of thousands of tons of carbon to the environment. Macrobenthic communities colonizing the recently opened shelf in the Larsen A and B bays may not have the chance to reach the type of mature assemblage inhabiting the eastern WS shelf. The highest temperatures derived from CDW intrusions were recorded in the Filchner-Ronne region, suggesting that the consequences of the thermal impact could develop faster here than in the rest of the WS. Thus, these macrobenthic communities may show the effects of warming earlier than those thriving in other regions of the WS shelf. Global warming seriously threats the abundant and highly diverse macrobenthic communities of the Antarctic continental shelf.
Phenological shifts, by initiating reproductive events earlier, in response to advanced seasonal warming is one of the most striking effects currently observed in wild populations. For sea turtles, phenological adjustment to warming conditions could be the most effective short-term adaptation option against climate change. We calculated future phenological changes required in seven important loggerhead (Caretta caretta) nesting populations to continue achieving a high hatching success and a sex ratio that lies within current ranges. Considering temperature-mediated phenological changes, we found that most populations (six out of seven) will not be able to keep pace with a warming climate. Under an optimistic climate warming scenario (RCP4.5), these populations will face a climatic debt, that is, a difference between required and expected phenological changes, and warming will substantially reduce hatching success and induce a feminization of hatchlings, which may jeopardize their reproductive sustainability. Our approach offers the possibility to quantify the efficiency of phenological shifts in oviparous reptiles by considering physiological, developmental and phenological processes.
Sea-surface temperature (SST) was one of the first ocean variables to be studied from earth observation satellites. Pioneering images from infrared scanning radiometers revealed the complexity of the surface temperature fields, but these were derived from radiance measurements at orbital heights and included the effects of the intervening atmosphere. Corrections for the effects of the atmosphere to make quantitative estimates of the SST became possible when radiometers with multiple infrared channels were deployed in 1979. At the same time, imaging microwave radiometers with SST capabilities were also flown. Since then, SST has been derived from infrared and microwave radiometers on polar orbiting satellites and from infrared radiometers on geostationary spacecraft. As the performances of satellite radiometers and SST retrieval algorithms improved, accurate, global, high resolution, frequently sampled SST fields became fundamental to many research and operational activities. Here we provide an overview of the physics of the derivation of SST and the history of the development of satellite instruments over half a century. As demonstrated accuracies increased, they stimulated scientific research into the oceans, the coupled ocean-atmosphere system and the climate. We provide brief overviews of the development of some applications, including the feasibility of generating Climate Data Records. We summarize the important role of the Group for High Resolution SST (GHRSST) in providing a forum for scientists and operational practitioners to discuss problems and results, and to help coordinate activities world-wide, including alignment of data formatting and protocols and research. The challenges of burgeoning data volumes, data distribution and analysis have benefited from simultaneous progress in computing power, high capacity storage, and communications over the Internet, so we summarize the development and current capabilities of data archives. We conclude with an outlook of developments anticipated in the next decade or so.
Numerous marine reserves worldwide are losing their ability to protect wild endemic species due to surrounding ecological deterioration caused by coastal landscape artificialization. Such risk of becoming invalid nature reserves is particularly high in China's Bohai Sea coastal zone, a region with rapid urbanization and industrialization. In this study, the ecological quality (EQ) status around Laizhou Bay Ostrea rivularis germplasm reserve (R1), Yellow River Estuary Meretrix meretrix germplasm reserve (R2), and Taoer Estuary Sinonovacula constricta germplasm reserve (R3) was dynamically diagnosed using seven indicators characterizing ecological support and threat from peripheral environments. A series of thresholds indicating EQ and corresponding landscape artificialization intensity (LAI) were determined based on multi-factor clustering analysis and relational regression simulation. The results show that the surroundings of these three reserves were favorable in 1984, insufficient in 2000, and unfavorable in 2015. With an average 7.5 times increase in LAI over the past three decades, the EQ levels around R1-R3 declined significantly and have deviated greatly from their optimal reference status by 2015, which stemmed mainly from intertidal landscape artificialization, such as establishing salt pans, industrial areas and ports after reclaiming wetlands. It was found that R3 > R1 > R2 in terms of overall peripheral ecological degradation, implying that the closer the marine reserve is to the land, the more likely it is to lose its effectiveness. The changes in EQ status and LAI were well indicated by the proportion of natural ecosystems, the distance between seawalls and protected boundaries, and the reserves' enclosed degree by artificial systems, which, as a quick and simple diagnostic approach, can facilitate spatial planning and management practices around marine reserves in the Bohai Sea coastal zone and elsewhere.
Bottom trawling is a common fishing method for harvesting demersal marine resources such as prawns and ground fish species. However, bottom trawling is known to have negative impacts on marine ecosystems and several measures have been suggested to sustainably manage the fishing method including, mapping trawling pressure and restricting its use away from fragile marine ecosystems. In this study, we map spatio-temporal distribution of trawling effort using 8900 trawls obtained from logbook statistical data and consequently evaluate the effectiveness of a Vessel Monitoring System (VMS) and a Prawn Fisheries Management Plan (PFMP) in the Malindi-Ungwana Bay, Kenya. The PFMP and VMS aimed at restricting prawn trawling to areas beyond 3 nm from shoreline since 2010 in order to reduce conflict with artisanal fishers. Results show spatio-temporal adjustments in the distribution of fishing effort and catch rates of prawns following regulatory changes in the bay. Encroachment in no-trawl areas occurred gradually between 2011 and 2017 with some years (2013, 2016) depicting over 50% of fishing effort in the no-trawl areas. Trawling within the restricted zone produced higher catch per unit effort (CPUE) of prawns compared to fishing outside the zone. Introduction of VMS in 2017 led to a significant reduction of fishing effort in no-trawl area of about 80% by 2018. The change in fleet behaviour in the bay after introduction of the VMS, provides important insights on how marine spatial planning and technology could be applied to enhance compliance with fishing area regulations, reduce resource use conflicts and promote sustainable fisheries.
The rate of change on coastlines is accelerating from climate change and coastal development. Coastal flooding is a particularly pressing and increasing problem, which affects hundreds of millions of people and damages trillions of US$ in property. Scientists, practitioners and managers must be able to quickly assess flood risk and identify appropriate adaptation and risk reduction measures often with limited data and tools, particularly in developing countries. To inform these decision-making processes, we identify how sensitive flood risk and adaptation analyses are to changes in the resolution of data and models. We further do these comparisons in the context of assess the benefits of an ecosystem-based approach for risk reduction. There is growing interest in these ecosystem-based approaches as cost effective measures for adaptation and risk reduction. We assess flood risks from tropical cyclones and the flood risk reduction benefits provided by mangroves in Pagbilao (the Philippines). Then, we also compare risks and risk reduction (benefits) using different quality data and models, to identify where to invest in in new modeling and data acquisition to improve decision-making. We find that coastal flood risk valuation improves by using high resolution topography and long time series of data on tropical cyclones, while flood reduction benefits of mangroves are better valued by using consistent databases and models along the whole process rather than investing in single measures.
Metal/metalloid concentrations in water sediment and commercial fishes of Loreto Maritime National Park (MNP), Baja California Sur, Mexico were determined for a comprehensive geochemical study. In-situ physical characteristics (pH, conductivity, redox potential, dissolved oxygen, turbidity) of water clearly indicated the unique oceanographic properties of the Gulf of California. Likewise, the distribution pattern of metals/metalloid in water, sediments and fishes denoted the influences of local geology, longshore currents, upwelling process, natural hydrothermal vents and the 100-year old mining activities of Santa Rosalia region, situated to the north of Loreto. Calculated carcinogenic indices in commercial fish species showed safe human consumption. Thus, the present research validates a comprehensive geochemical study of protected areas upholding the need for continuous monitoring for a better conservation of coastal ecosystems.
The community of species, human institutions, and human activities at a given location have been shaped by historical conditions (both mean and variability) at that location. Anthropogenic climate change is now adding strong trends on top of existing natural variability. These trends elevate the frequency of “surprises”—conditions that are unexpected based on recent history. Here, we show that the frequency of surprising ocean temperatures has increased even faster than expected based on recent temperature trends. Using a simple model of human adaptation, we show that these surprises will increasingly challenge natural modes of adaptation that rely on historical experience. We also show that warming rates are likely to shift natural communities toward generalist species, reducing their productivity and diversity. Our work demonstrates increasing benefits for individuals and institutions from betting that trends will continue, but this strategy represents a radical shift that will be difficult for many to make.
There is growing evidence indicating that variability and extremes in conditions in the marine environment are as (or more) important as changes in the mean for determining threats to biodiversity, impacts on ecosystem services, and consequences for human systems (1⇓⇓–4). With respect to ocean temperature, long-term persistent warming has been accompanied by an increased frequency of discrete periods of extreme regional ocean warming (marine heatwaves) (5). This poses a threat to biodiversity and ecosystem services, including impacts on foundation species (corals, seagrasses, and kelps) (1, 4). The potential of human and natural systems to adapt to such changes remains unclear. In PNAS, Pershing et al. (6) show that an increasing frequency of extreme heat events—or “surprises”—is challenging autonomous modes of adaptation that rely on historical experience. The authors contrast reactive adaptation that is guided by experiences of past events with proactive adaptation based on forward-looking decision making. They use ocean ecosystems as a case study and, based on mathematical models, consider how temperature trends and the frequency of surprise (high) temperature events could impact natural and human communities under different adaptation strategies.
Invasive predators have caused rapid declines in many native prey species across the globe. Predator invasion success may be attributed to prey naïveté, or the absence of anti-predator behavior between native and non-native species. An understanding of the effects of naïveté at different timescales since introduction and across multiple trophic levels is lacking, however, particularly in marine systems. Given the central role of trophic interactions in invasion dynamics, this knowledge gap limits the ability to predict high impact predator invasions. Naïveté was examined across three trophic levels of marine invertebrates: a native basal prey (hard clam), two non-native intermediate predators (the recently-introduced Asian shore crab and the long-established European green crab), a native intermediate predator (juvenile blue crabs), and a native top predator (adult blue crab). We hypothesized that naïveté would be more pronounced in trophic interactions involving the recently-introduced non-native predator in comparison to the long-established non-native and native intermediate predators. We further hypothesized that the recently-introduced intermediate predator would both benefit from naïveté of the native basal prey and be hindered by higher mortality through its own naïveté to the native top predator. To test these hypotheses, three laboratory experiments and a field experiment were used. Consistent with our hypotheses, basal prey naïveté was most pronounced with the recently-introduced intermediate predator, and this increased the predator’s foraging success. This recently-introduced intermediate predator, however, exhibited an ineffective anti-predator response to the native top predator, and was also preyed upon more in the field than its long-established and native counterparts. Therefore, despite direct benefits from basal prey naïveté, the recently-introduced intermediate predator’s naïveté to its own predators may limit its invasion success. These results highlight the importance of a multi-trophic perspective on predator-prey dynamics to more fully understand the consequences of naïveté in invasion biology.
Infectious diseases are potential contributors to decline in Coho salmon (Oncorhynchus kisutch) populations. Although pathogens are theoretically considered to pose higher risk in high-density rearing environments like hatcheries, there is no direct evidence that hatchery-origin Coho salmon increase the transmission of infectious agents to sympatric wild populations. This study was undertaken to compare prevalence, burden, and diversity of infectious agents between hatchery-reared and wild juvenile Coho salmon in British Columbia (BC), Canada. In total, 2,655 juvenile Coho salmon were collected between 2008 and 2018 from four regions of freshwater and saltwater in BC. High-throughput microfluidics qPCR was employed for simultaneous detection of 36 infectious agents from mixed-tissue samples (gill, brain, heart, liver, and kidney). Thirty-one agents were detected at least once, including ten with prevalence >5%. Candidatus Brachiomonas cysticola, Paraneuclospora theridion, and Parvicapsula pseudobranchiocola were the most prevalent agents. Diversity and burden of infectious agents were substantially higher in marine environment than in freshwater. In Mainland BC, infectious burden and diversity were significantly lower in hatchery smolts than in wild counterparts, whereas in other regions, there were no significant differences. Observed differences in freshwater were predominantly driven by three parasites, Loma salmonae, Myxobolus arcticus, and Parvicapsula kabatai. In saltwater, there were no consistent differences in agent prevalence between hatchery and wild fish shared among the west and east coasts of Vancouver Island. Although some agents showed differential infectious patterns between regions, annual variations likely contributed to this signal. Our findings do not support the hypothesis that hatchery smolts carry higher burdens of infectious agents than conspecific wild fish, reducing the potential risk of transfer to wild smolts at this life stage. Moreover, we provide a baseline of infectious agents in juvenile Coho salmon that will be used in future research and modeling potential correlations between infectious profiles and marine survival.
Ocean acidification and ocean warming (OAW) are simultaneously occurring and could pose ecological challenges to marine life, particularly early life stages of fish that, although they are internal calcifiers, may have poorly developed acid-base regulation. This study assessed the effect of projected OAW on key fitness traits (growth, development and swimming ability) in European sea bass (Dicentrarchus labrax) larvae and juveniles. Starting at 2 days post-hatch (dph), larvae were exposed to one of three levels of PCO2 (650, 1150, 1700 μatm; pH 8.0, 7.8, 7.6) at either a cold (15°C) or warm (20°C) temperature. Growth rate, development stage and critical swimming speed (Ucrit) were repeatedly measured as sea bass grew from 0.6 to ~10.0 (cold) or ~14.0 (warm) cm body length. Exposure to different levels of PCO2 had no significant effect on growth, development or Ucrit of larvae and juveniles. At the warmer temperature, larvae displayed faster growth and deeper bodies. Notochord flexion occurred at 0.8 and 1.2 cm and metamorphosis was completed at an age of ~45 and ~60 days post-hatch for sea bass in the warm and cold treatments, respectively. Swimming performance increased rapidly with larval development but better swimmers were observed in the cold treatment, reflecting a potential trade-off between fast grow and swimming ability. A comparison of the results of this and other studies on marine fish indicates that the effects of OAW on the growth, development and swimming ability of early life stages are species-specific and that generalizing the impacts of climate-driven warming or ocean acidification is not warranted.
Due to climate change, coral reefs have experienced mass bleaching, and mortality events in recent years. Although coral reefs are unlikely to persist in their current form unless climate change can be addressed, local management can have a role to play by extending the time frame over which there are functional reef systems capable of recovery. Here we consider the potential application of one form of local management – management of herbivorous fishes. The premise behind this approach is that increased herbivory could shift reef algal assemblages to states that are benign or beneficial for corals, thereby increasing corals’ ability to recover from destructive events such as bleaching and to thrive in periods between events. With a focus on Indo-Pacific coral reefs, we review what is known about the underlying processes of herbivory and coral-algal competition that ultimately affect the ability of corals to grow, persist, and replenish themselves. We then critically assess evidence of effectiveness or otherwise of herbivore management within marine protected areas (MPAs) to better understand why many MPAs have not improved outcomes for corals, and more importantly to identify the circumstances in which that form of management would be most likely to be effective. Herbivore management is not a panacea, but has the potential to enhance coral reef persistence in the right circumstances. Those include that: (i) absent management, there is an “algal problem” – i.e., insufficient herbivory to maintain algae in states that are benign or beneficial for corals; and (ii) management actions are able to increase net herbivory. As increased corallivory is a potentially widespread negative consequence of management, we consider some of the circumstances in which that is most likely to be a problem as well as potential solutions. Because the negative effects of certain algae are greatest for coral settlement and early survivorship, it may be that maintaining sufficient herbivory is particularly important in promoting recovery from destructive events such as mass bleaching. Thus, herbivore management can have a role to play as part of a wider strategy to manage and reduce the threats that currently imperil coral reefs.
In 2012, California completed its marine protected area (MPA) planning and designation process, yielding a network of 124 MPAs from the Mexican border to Oregon. The management effort that has followed is comprehensive and strategic, with a focus on scientific monitoring, interagency coordination, public education and outreach, and enforcement. Initial monitoring results show more and bigger fish, especially in older MPAs where the benefits of limiting fishing have had longer to accrue. Today, California state agencies increasingly acknowledge and contemplate MPA protections in their permitting decisions, as regional and statewide outreach and education efforts enhance public awareness, social capital and stewardship. While enforcement remains challenging in a marine region as large and populous as California, the state has taken important steps to promote compliance with new MPA regulations and—with the support of the state legislature—has strengthened laws to address poaching. As new MPAs are established throughout the world in accordance with global targets, California's post-designation efforts provide a valuable and educational case study for local, national and international MPA managers.
Active hydrothermal vents are valued worldwide because of the importance of their biodiversity and their influence on scientific discovery and insight about life on Earth and elsewhere in the Universe. There exist at least 20 areas and area networks with conservation measures for deep-sea hydrothermal vents, established by 12 countries and three Regional Fisheries Management Organisations, in six oceanic regions. Area-based management tools (ABMT) implemented by these countries illustrate multiple categories and means of protection and management of these rare and vulnerable habitats. Some ABMTs only regulate bottom and deep-trawling fisheries activities, others manage additional activities such as mining, scientific research, and bioprospecting, while still others protect active hydrothermal vents through broad conservation interventions. This atlas summarizes the “who”, “what”, “when”, “where” of protected hydrothermal vents worldwide and underscores recognition of the importance of hydrothermal-vent ecosystems by coastal States.
The governance frameworks for Ningaloo Marine Park (NMP) and Shark Bay Marine Park (SBMP) are explored, employing the MPA governance analysis framework. Both face similar conflicts typical of ecotourism, particularly related to the impacts of recreational fishing and marine wildlife tourism. A high diversity of incentives is found to be used, the combination of which promotes effectiveness in achieving conservation objectives and equity in governance. Highly evolved regulations have provided for depleted spangled emperor (Lethrinus nebulosus) stocks in NMP to stabilise and begin recovery, and pink snapper (Pagrus auratus) stocks in SBMP to recover from past depletions, though there are still concerns about recreational fishing impacts. The governance frameworks for marine wildlife tourism are considered extremely good practice. Some incentives need strengthening in both cases, particularly capacity for enforcement, penalties for deterrence and cross-jurisdictional coordination. In NMP there was also a need to promote transparency in making research and monitoring results available, and to address tensions with the recreational fishing sector by building linkages to provide for their specific representation, as part of a strategy to build trust and cooperation with this sector. Both case studies represent world-leading good practice in addressing proximal impacts from local activities, but in the longer-term the foundation species of both marine parks are critically threatened by the distal impacts of climate change. A diversity of incentives has promoted resilience in the short-term, but global action to mitigate climate change is the only way to promote the long-term resilience of these iconic marine ecosystems.
Marine Protected Areas (MPAs) are a widely used and flexible policy tool to help preserve marine biodiversity. They range in size and governance complexity from small communally managed MPAs, to massive MPAs on the High Seas managed by multinational organizations. As of August 2018, the Atlas of Marine Protection (MPAtlas.org) had catalogued information on over 12,000 Marine Protected Areas. We analyzed this global database to determine groups of MPAs whose characteristics best distinguished the diversity of MPA attributes globally, based upon our comprehensive sample. Groups were identified by pairing a Principal Components Analysis (PCA) with a k-means cluster analysis using five variables; age of MPA, area of MPA, no-take area within MPA, latitude of the MPA's center, and Human Development Index (HDI) of the host country. Seven statistically distinct groups of MPAs emerged from this analysis and we describe and discuss the potential implications of their respective characteristics for MPA management. The analysis yields important insights into patterns and characteristics of MPAs around the world, including clusters of especially old MPAs (greater than 25 and 66 years of age), clusters distributed across nations with higher (HDI ≥ 0.827) or lower (HDI ≤ 0.827) levels of development, and majority no-take MPAs. Our findings also include statistical verification of Large Scale Marine Protected Areas (LSMPAs, approximately >180,000km2) and a sub-class of LSMPA's we call “Giant MPAs” (GMPAs, approximately >1,000,000km2). As a secondary outcome, future research may use the clusters identified in this paper to track variability in MPA performance indicators across clusters (e.g., biodiversity preservation/restoration, fish biomass) and thereby identify relationships between cluster and performance outcomes. MPA management can also be improved by creating communication networks that connect similarly clustered MPAs for sharing common challenges and best practices.
Climate change and dramatic change to ocean ecosystems are two of the leading indicators of the proposed ‘Anthropocene’ epoch. As knowledge of feedbacks between climate change and damage to ocean ecosystems has improved, the case for addressing these interrelated challenges concurrently has strengthened. This chapter begins by reviewing the relationship between climate change and the state of the ocean as explained in recent scientific publications. It proceeds from this to summarise how this ocean-climate nexus is addressed in current and developing international law, before focusing on three particular examples: first, regulation of international shipping emissions; second, management of coastal ecosystems (‘blue carbon’); and third, the current negotiation on a new treaty to protect the high seas. These three examples illustrate the diversity of regulation undertaken within a four-square matrix of processes under the Climate Convention, or under the Law of the Sea Convention, which are based on either mandatory commitments or non-binding facilitative measures. The chapter concludes that there are further opportunities to address ocean-climate feedbacks in a targeted and timely manner, including through additional linkages between UNFCCC- and UNCLOS-based processes.
Throughout the world coral reefs are being degraded at unprecedented rates. Locally, reefs are damaged by pollution, nutrient overload and sedimentation from out-dated land-use, fishing and mining practices. Globally, increased greenhouse gases are warming and acidifying oceans, making corals more susceptible to stress, bleaching and newly emerging diseases. The coupling of climate change impacts and local anthropogenic stressors has caused a widespread and well-recognized reef crisis. While the establishment and enforcement of marine protected areas and preventing the acceleration of climate change are essential to management of these stressors, the inexorable impacts of climate change will continue to cause declines in genetic diversity and population viability. Gamete cryopreservation has already acted as an effective insurance policy to maintain the genetic diversity of many wildlife species, and has now begun to be explored and applied to coral conservation. Cryopreservation can act to preserve reef biodiversity and genetic diversity. To date, we have had a great deal of success with cryopreserving sperm from ~30 coral species of coral species. Moreover, we are creating the basic science to freeze and thaw coral larvae that can soon be used to help secure and restore reefs. Building on these successes, we have established genetic banks using frozen samples and use those samples to help mitigate threats to the Great Barrier Reef and other areas.