- Globally, coral reef monitoring programmes conducted by volunteer-based organizations or local communities have the potential to collect large quantities of marine data at low cost. However, many scientists remain sceptical about the ability of these programmes to detect changes in marine systems when compared with professional techniques. A limited number of studies have assessed the efficacy and validity of volunteer-based monitoring, and even fewer have assessed community-based methods. This study in Cambodia investigated the ability of surveyors of different levels of experience to conduct underwater surveys using a simple coral reef methodology. Surveyors were assigned to four experience categories and conducted a series of six 20 × 5 m belt transects using five benthic indicator species. Results show decreased variation in marine community assessments with increasing experience, indicating that experience, rather than cultural background, influences survey ability. This suggests that locally based programmes can fill gaps in knowledge with suitable ongoing training and assessment.
Cold-water coral (CWC) habitats can form complex structures which provide refuge, nursery grounds and physical support for a diversity of other living organisms, but despite their ecological significance, CWCs are still vulnerable to human pressures such as fishing, pollution, ocean acidification and global warming
Providing coherent and representative conservation of vulnerable marine ecosystems including CWCs is one of the aims of the Marine Protected Areas networks being implemented across European seas and oceans under the EC Habitats Directive, the Marine Strategy Framework Directive and the OSPAR Convention. In order to adequately represent ecosystem diversity these initiatives require a standardised habitat classification that organises the variety of biological assemblages and provides consistent and functional criteria to map them across European Seas (Howell 2010). One such classification system, EUNIS, enables a broad level classification of the deep sea based on abiotic and geomorphological features. More detailed lower biotope-related levels are currently under-developed, particularly with regards deep-water habitats (>200 m depth).
This paper proposes a hierarchical CWC biotope classification scheme that could be incorporated by existing classification schemes such as EUNIS. The scheme was developed within the EU FP7 project CoralFISH to capture the variability of CWC habitats identified using a wealth of seafloor imagery datasets from across European seas and oceans. Depending on the resolution of the imagery being interpreted, this hierarchical scheme allows data to be recorded from broad CWC biotope categories down to detailed taxonomy-based levels, thereby providing a flexible yet valuable information level for management. The CWC biotope classification scheme identifies 81 biotopes and highlights the limitations of the classification framework and guidance provided by EUNIS, the EC Habitats Directive, OSPAR and FAO; with limited categories for identifying and classifying these CWC habitats.
The disruption of the coral–algae symbiosis (coral bleaching) due to rising sea surface temperatures has become an unprecedented global threat to coral reefs. Despite decades of research, our ability to manage mass bleaching events remains hampered by an incomplete mechanistic understanding of the processes involved. In this study, we induced a coral bleaching phenotype in the absence of heat and light stress by adding sugars. The sugar addition resulted in coral symbiotic breakdown accompanied by a fourfold increase of coral-associated microbial nitrogen fixation. Concomitantly, increased N:P ratios by the coral host and algal symbionts suggest excess availability of nitrogen and a disruption of the nitrogen limitation within the coral holobiont. As nitrogen fixation is similarly stimulated in ocean warming scenarios, here we propose a refined coral bleaching model integrating the cascading effects of stimulated microbial nitrogen fixation. This model highlights the putative role of nitrogen-fixing microbes in coral holobiont functioning and breakdown.
Coral reefs serve as natural barriers that protect adjacent shorelines from coastal hazards such as storms, waves, and erosion. Projections indicate global degradation of coral reefs due to anthropogenic impacts and climate change will cause a transition to net erosion by mid-century. Here, we provide a comprehensive assessment of the combined effect of all of the processes affecting seafloor accretion and erosion by measuring changes in seafloor elevation and volume for five coral reef ecosystems in the Atlantic, Pacific, and Caribbean over the last several decades. Regional-scale mean elevation and volume losses were observed at all five study sites and in 77 % of the 60 individual habitats that we examined across all study sites. Mean seafloor elevation losses for whole coral reef ecosystems in our study ranged from −0.09 to −0.8 m, corresponding to net volume losses ranging from 3.4 × 106 to 80.5 × 106 m3 for all study sites. Erosion of both coral-dominated substrate and non-coral substrate suggests that the current rate of carbonate production is no longer sufficient to support net accretion of coral reefs or adjacent habitats. We show that regional-scale loss of seafloor elevation and volume has accelerated the rate of relative sea level rise in these regions. Current water depths have increased to levels not predicted until near the year 2100, placing these ecosystems and nearby communities at elevated and accelerating risk to coastal hazards. Our results set a new baseline for projecting future impacts to coastal communities resulting from degradation of coral reef systems and associated losses of natural and socioeconomic resources.
Species distribution modelling can be applied to identify potentially suitable habitat for species with largely unknown distributions, such as many deep-water corals. Important variables influencing species occurrence in the deep sea, e.g. substrate composition, are often not included in these modelling approaches because high-resolution data are unavailable. We investigated the relationship between substrate composition and the occurrence of the two deep-water octocoral species Primnoa resedaeformis and Paragorgia arborea, which require hard substrate for attachment. On a scale of 10 s of metres, we analysed images of the seafloor taken at two locations inside the Northeast Channel Coral Conservation Area in the Northwest Atlantic. We interpolated substrate composition over the sampling areas and determined the contribution of substrate classes, depth and slope to describe habitat suitability using maximum entropy modelling (Maxent). Substrate composition was similar at both sites - dominated by pebbles in a matrix of sand (>80%) with low percentages of suitable substrate for coral occurrence. Coral abundance was low at site 1 (0.9 colonies of P. resedaeformis per 100 m2) and high at site 2 (63 colonies of P. resedaeformis per 100 m2) indicating that substrate alone is not sufficient to explain varying patterns in coral occurrence. Spatial interpolations of substrate classes revealed the difficulty to accurately resolve sparsely distributed boulders (3 – 5% of substrate). Boulders were by far the most important variable in the habitat suitability model (HSM) for P. resedaeformis at site 1, indicating the fundamental influence of a substrate class that is the least abundant. At site 2, HSMs identified cobbles and sand/pebble as the most important variables for habitat suitability. However, substrate classes were correlated making it difficult to determine the influence of individual variables. To provide accurate information on habitat suitability for the two coral species, substrate composition needs to be quantified so that small fractions (<20% contribution of certain substrate class) of suitable substrate are resolved. While the collection and analysis of high-resolution data is costly and spatially limited, the required resolution is unlikely to be achieved in coarse-scale interpolations of substrate data.
Coral reefs are degraded by the synergistic action of climate and anthropogenic stressors. Coral cover in the Palk Bay reef at the northern Indian Ocean largely declined in the past decade due to frequent bleaching events, tsunami and increased fishing activities. In this study, we carried out a comparative assessment to assess the differences in the recovery and resilience of three spatially distant reefs viz. Vedhalai, Mandapam and Pamban along Palk Bay affected by moderate, severe and low fishing pressure respectively. The assessment was based on the juvenile coral recruitment pattern and its survivability combined with availability of hard substratum, live coral cover and herbivore reef fish stock. The Vedhalai reef has the highest coral cover (14.6 ± 6.3%), and ≥90% of the live corals in Vedhalai and Mandapam were affected by turf algal overgrowth. The density of herbivore reef fish was low in Vedhalai and Mandapam reefs compared to the Pamban reef with relatively few grazing species. The juvenile coral diversity and density were high in the Pamban reef and low in Vedhalai and Mandapam reefs despite high hard substratum cover. In total, 22 species of juvenile corals of 10 genera were recorded in Palk Bay. Comparison of the species diversity of juvenile corals with adult ones suggested that the Pamban reef is connected with other distant reefs whereas Vedhalai and Mandapam reefs were self-seeded. There was no statistically significant difference in the survivability of juvenile corals between the study sites, and in total, ≥90% of the juvenile corals survived the high sedimentation stress triggered by the northeast monsoon and bleaching stress that occurred recurrently. Our results indicated that the human activities indirectly affected the juvenile coral recruitment by degrading the live coral cover and contributed to the spatial variation in the recovery and resilience of the Palk Bay reef. Low species diversity of the juvenile corals will increase the vulnerability of the Palk Bay reef to species-specific endemic threats.
Despite their high value, the future of coral reefs is currently in jeopardy. Recent studies have shown that many reefs worldwide have lost 50–90% of live coral over the past 30–40 years (Baker 2014). Corals are dying worldwide as a result of multiple stressors, many of them human-induced (Pandolfi 2003). Conservation and restoration of coral reef habitats are key to their future and the future of nations that depend on them, including the United States. An important part of any conservation effort must be to reduce or eliminate the stressors that are causing reefs to become degraded. This article will outline some of the major threats to coral reefs and the strategies that everyone, whether living one mile or one thousand miles from a coral reef, can use to help reduce negative impacts on these ecosystems and preserve their services for years to come.
Coralline algae provide important ecosystem services but are susceptible to the impacts of ocean acidification. However, the mechanisms are uncertain, and the magnitude is species specific. Here, we assess whether species-specific responses to ocean acidification of coralline algae are related to differences in pH at the site of calcification within the calcifying fluid/medium (pHcf) using δ11B as a proxy. Declines in δ11B for all three species are consistent with shifts in δ11B expected if B(OH)4− was incorporated during precipitation. In particular, the δ11B ratio in Amphiroa anceps was too low to allow for reasonable pHcf values if B(OH)3 rather than B(OH)4− was directly incorporated from the calcifying fluid. This points towards δ11B being a reliable proxy for pHcf for coralline algal calcite and that if B(OH)3 is present in detectable proportions, it can be attributed to secondary postincorporation transformation of B(OH)4−. We thus show that pHcf is elevated during calcification and that the extent is species specific. The net calcification of two species of coralline algae (Sporolithon durum, and Amphiroa anceps) declined under elevated CO2, as did their pHcf. Neogoniolithon sp. had the highest pHcf, and most constant calcification rates, with the decrease in pHcf being ¼ that of seawater pH in the treatments, demonstrating a control of coralline algae on carbonate chemistry at their site of calcification. The discovery that coralline algae upregulate pHcf under ocean acidification is physiologically important and should be included in future models involving calcification.
Marine protected areas (MPAs) are being successful in the management of fishing resources and conservation of biodiversity in many parts of the world. The assessment of the management effectiveness provides examples to improve the management of these areas. Thus, this study assessed the management effectiveness of 11 MPAs with reef environments in the coast of Brazil, in the period of 10 years (2005, 2010, and 2015), through the method of Rapid Assessment and Priorization of Protected Area Management (RAPPAM). The questionnaire was also used to address the pressure (activities that affect the MPA in the last 5 years) and threats (activities that can potentially affect the MPA in the next 5 years. From the 11 MPAs assessed, the highest values of pressures and threats were obtained for two areas in the year of 2005 and four areas in 2015 (above 35%). The mean management effectiveness between 2005 and 2015 increased from 55.6% (±8.2) in 2005 to 60% (±11.5) in 2015. However, even with this increase, the mean effectiveness of some MPAs is still below the limit considered ideal for satisfactory management (<40%), and the number of MPAs with good management (>60%) has not changed over time.
Data from real-time sensor networks along the Great Barrier Reef (GBR) over the 2015–2016 austral summer showed that reef water temperatures exceeded empirical coral bleaching thresholds at a number of sites. Temperatures in the southern GBR were within historically normal limits with temperatures below the empirical bleaching threshold. The central GBR just reached the empirical bleaching threshold while, in the north, Lizard Island recorded four consecutive days above the bleaching threshold. Thursday Island in the far northern GBR experienced 10 days above the bleaching threshold. The in situ data predicted only slight bleaching in the southern GBR, moderate bleaching in the central GBR, widespread bleaching in the north and severe bleaching in the far north, which compares well with the initial survey data. Peak temperatures occurred later in the year in the north (mid-March 2016) than in the south (early February 2015) with temperatures remaining above the long-term mean well into the austral autumn. Comparison against satellite sea surface temperature data highlighted issues of cloud cover with data only being available for 30–40% of days over the summer. While the agreement with the in situ data was good, the satellite data missed fine-scale events and under-estimated the event at Thursday Island.