Coastal Reefs Research Articles

Identifying innovation discourses for nitrogen management in the sugarcane sector in Great Barrier Reef catchments using Q-methodology

Dissolved inorganic nitrogen (DIN) run-off from sugarcane farms along Australia's Great Barrier Reef (GBR) coast is implicated in poor catchment water quality and putting pressure on reef health. Reducing DIN is the focus of innovative policies to cut pollution and to maximize social benefit across economic sectors. We use Q-methodology to gain insight into discourses present amongst sugarcane sector stakeholders in GBR catchments. Issue statements, which we aligned with concepts from the Theory of Planned Behaviour, were ranked and correlations identified to generate factors that informed our descriptions of discourses. We found four discourse groups we called sector stalwarts, scientific rationalists, economic maximisers, and sector defenders. We also collected respondent demographic data from which we could judge the propensities of respondent groups to identify with different discourses. This information can help industry innovators and policymakers identify the attributes, mindsets, and appropriate language metaphors for engaging stakeholders in reducing catchment pollution.

Spatial variation of cadmium concentration in the bivalve Beguina semiorbiculata (Linnaeus, 1758) from coastal coral reefs of Vietnam

The spatial distribution of trace metals (Fe, Zn, Cu, Cd, Mn, Pb and Ni) in the soft tissues of Beguina semiorbiculata from coastal reefs of Vietnam was studied. Bivalves were collected in May 2013 from 22 sites along the south-eastern coast from Gulf of Thailand to Ha Long Bay.The most increased concentrations of studied metals (excluding Cd) were shown in the B. semiorbiculata living in Ha Long Bay characterized by terrestrial runoff and anthropogenic effects. In contrast, the maximal Cd concentrations were found in the bivalves from coastal reefs of central Vietnam and Gulf of Thailand.Apparently, Cd concentration depends on seasonal upwellings (central part of Vietnam coast) and composition of suspended matter (Gulf of Thailand). Consequently, Cd distribution in the coastal waters of Vietnam should be strongly controlled in relation with predicted risk of climate change that may further significantly increased Cd bioavailability for habitants of coral reefs.

Sedimentary nitrogen dynamics in a coastal reef area with relatively high nitrogen concentration

Sedimentary nitrogen dynamics in a coastal reef area with relatively high nitrogen concentration

Functional vulnerability and biogeography of reef fish assemblages in the Galapagos Archipelago

The Galapagos archipelago's unique reef biodiversity and fish distribution patterns are well documented. However, reef ecosystem vulnerability to losing functional diversity and the biogeographical drivers of community functional diversity are undescribed. The functional diversity and vulnerability of coastal reef fish communities in the Galapagos were investigated using Baited Remote Underwater Stereo-Video systems (stereo-BRUVs). Relative abundance data for 41,594 individual fish belonging to 121 species was collected, 87 functional entities were identified, and functional diversity and vulnerability estimated based on five functional traits. The influence of spatial and environmental variability and human impact on functional entity composition and richness were also assessed.Galapagos reef fish communities have a high vulnerability to reduced functional diversity if species are lost due to the low redundancy and high sensitivity of reef fish functional entities. However, there may be some ecosystem resilience against species loss from species filling ecologically similar niches instead of redundant species filling the same niche. The functional trait structure and vulnerability of Galapagos reef fish assemblages reflect the known trophic structure of the marine food web. Most functional entities with resilience from redundancy include upper trophic level species with piscivorous diets. Most functional entities that are sensitive and represented by only one species include lower trophic level species. Spatial variables relating to marine environmental variation (from tropical to temperate reef ecosystems) and benthic habitat bottom incline were important predictors of reef fish functional entity distribution. Functional vulnerability may be a concern in marine ecosystems where functional diversity is low, including at higher southern latitudes and western longitudes, the cooler temperate regions and topographically simple marine habitats. Our study raises concerns about the long-term functioning of Galapagos marine ecosystems under present climate change and human management scenarios. We suggest grouping species by functional traits for consideration in the future marine management of Galapagos marine communities.

Predicting the current and future suitable-habitat distribution of tropical adult and juvenile targeted fishes in multi-sector fisheries of central Queensland, Australia

Context Coastal and estuarine finfish species are responding to human-induced climate change by altering their distributions. In tropical regions, the species mostly affected by warming have limited acclimation capacity or live close to their upper thermal limits. Consequently, coastal fish assemblages may dramatically contract in range, experience declining population abundance or local extinction. Aim Here we use two different predictive modelling techniques that cope with non-linear empirical relationships between responses and environmental predictors to investigate distribution change. Methods The habitat-suitability models we use are the maximum entropy model (MaxEnt) and the generalised additive model (GAM). We built the models for the period 2004–2019 with environmental data relevant to coastal systems. We incorporated climate change at current conditions, near future (2015–2054) and distant future (2055–2100) from CMIP6 climate models. Key results We identified bathymetry and sea-surface temperature to be key variables explaining the current and future distribution of coastal finfish and elasmobranchs of the Great Barrier Reef coast in central Queensland. Conclusions We showed how the distributions of valuable fisheries species will change under future warming conditions. Implications The objective is to inform fisheries management supporting the restructure of existing fisheries or the development of new resources for the dual purposes of conservation and food security.

Characteristics and evaluation of coastal erosion vulnerability of typical coast on Hainan Island

Coastal erosion vulnerability assessment is widely used to assess the loss degree of coastal zone caused by erosion, and plays an important role in coastal natural resources protection, planning, management and decision-making. Based on the natural and social characteristics of the east coast of Qiongdong and the coastal erosion vulnerability index (CVI) method, this study selected 8 assessment indicators, such as shoreline change rate (U1). The Delphi method and the entropy weight method were used to calculate the comprehensive index weight, combined with CVI method and geographic information system (GIS) technology, to quantitatively evaluate the temporal and spatial distribution characteristics of typical coastal erosion vulnerability such as coral reefs in the east of Hainan Island. The study area was divided into 5 grades: very low (31%), low (10%), moderate (28%), high (24%) and high vulnerability (7%), and the overall performance was moderate erosion vulnerability. The research showed that the interannual downward rate erosion of beach (U3) and the rate of change of the isobath (U2) of the beach were the main controlling factors affecting the vulnerability of coastal erosion in the study area, and the coastal dynamic factor had a greater impact than the other two factors. As a natural barrier, the coral reefs in the study area had good wave absorption and energy reduction, and the coral reef coasts showed low coastal erosion vulnerability, due to the complex hydrodynamic characteristics, estuary coasts is the most vulnerable areas. The verification results of the ROC-AUC method showed that the accuracy of erosion vulnerability was 68.9%, which provided an important reference for the ecological restoration of tropical coral reef biological coasts and the development and management of the Hainan Qiongdong coastal zone.

New insights on the Late Quaternary evolution of Abrolhos reefs, Eastern Brazilian Shelf

The Abrolhos shelf, in the eastern Brazilian margin, encompasses the largest reef province in the South Atlantic, characterised by low coral diversity and a high level of endemism. Knowledge gaps about how the Abrolhos coastal reefs evolved, during the post LGM and MIS 6/MIS 5, favoured a paradigm that is revisited in the light of new data. Here, new data from two new, long boreholes (20 and 50 m-long) are presented in order to investigate and provide new insights into the evolution of two shallow reefs on the Abrolhos Shelf during the late Pleistocene and Holocene epochs. Results show that Holocene and Pleistocene reefs grew on highly turbid waters with a significant terrigenous sediment input. Corals and CCA assemblages were identified as main framework builders of Abrolhos inner-shelf reefs since the Pleistocene. No clear shallowing upward sequence of reef builders was observed, which differs from other reef sequences all over the world. In terms of Holocene reef growth, Pedra Grande and Coroa Vermelha reefs turned on roughly coevally at different depths and with different coral assemblages. Pedra Grande reef started growing circa 6.8 kyr BP in a water depth approximately 10 m deeper than Coroa Vermelha, which started growing around 6.4 kyr BP, but Coroa Vermelha turned off at around 4 kyr BP, while Pedra Grande kept growing until around 1.2 kyr BP. This novel reef stratigraphy data provided a new insight on the evolution of the Abrolhos coastal reefs, showing that different environmental and topographic controls could have acted spatially in different ways. Coroa Vermelha reef seems to have started its growth as a result of a topographic high control. Pedra Grande reef seems to be connected to a broader submerged reef setting and started to grow in deeper water depths. The presence of three reef arcs in Abrolhos is proposed, including a submerged reef arc.

Neogene and Quaternary reef terraces of Mangaia, Rarotonga and Aitutaki (southern Cook Islands, South Pacific) revisited: gauges of sea-level change and island uplift?

New sedimentological data of facies and diagenesis as well as chronological data including strontium (87Sr/86Sr)-isotope ratios and uranium (U)-series dating, radiocarbon (14C) accelerator mass spectrometry (AMS) dating and biostratigraphy from elevated reef terraces (makatea) in the southern Cook Islands of Mangaia, Rarotonga and Aitutaki contribute to controversial discussions regarding age and sea-level relationships of these occurrences during the Neogene and Quaternary. The oldest limestones of the uplifted makatea island of Mangaia include reef-related facies which are mid-Miocene in age, based on new Sr-isotope and biostratigraphical data. In between these older deposits and the lowest coastal reef terrace of marine isotope stage (MIS) 5e, various older Pleistocene reef-related facies were identified. Based on Sr-isotope ratios, these were deposited during earlier Pleistocene highstands (as old as 2.28 Ma). Rare reef terraces on Rarotonga belong to the Plio-Pleistocene and the late Miocene, according to 87Sr/86Sr ratios. The late Miocene age is enigmatic as it exceeds the age of subaerially exposed volcanic rocks of Rarotonga island. The fossil reef could have formed on an older submarine volcanic high that was later displaced by younger volcanism to its present position, or the Sr-age could be too old due to diagenetic resetting. The Plio-Pleistocene Rarotonga reef terraces are overlain irregularly by Holocene reef deposits that are interpreted as storm rubble. Reef terraces on Aitutaki represent evidence of a higher-than-present (up to 1 m) sea-level during the late Holocene, based on 14C AMS age data. They are very similar to elevated late Holocene reefs of adjacent French Polynesia with regard to composition, elevation and age.

The Blob marine heatwave transforms California kelp forest ecosystems

Ocean warming has both direct physiological and indirect ecological consequences for marine organisms. Sessile animals may be particularly vulnerable to anomalous warming given constraints in food acquisition and reproduction imposed by sessility. In temperate reef ecosystems, sessile suspension feeding invertebrates provide food for an array of mobile species and act as a critical trophic link between the plankton and the benthos. Using 14 years of seasonal benthic community data across five coastal reefs, we evaluated how communities of sessile invertebrates in southern California kelp forests responded to the “Blob”, a period of anomalously high temperatures and low phytoplankton production. We show that this event had prolonged consequences for kelp forest ecosystems. Changes to community structure, including species invasions, have persisted six years post-Blob, suggesting that a climate-driven shift in California kelp forests is underway.

Organochlorine pesticides (OCPs) in corals and plankton from a coastal coral reef ecosystem, south China sea

Recent studies have indicated that coral mucus plays an important role in the bioaccumulation of a few organic pollutants by corals, but no relevant studies have been conducted on organochlorine pesticides (OCPs). Previous studies have also indicated that OCPs widely occur in a few coral reef ecosystems and have a negative effect on coral health. Therefore, this study focused on the occurrence and bioaccumulation of a few OCPs, such as dichlorodiphenyltrichloroethanes (DDTs), hexachlorobenzene (HCB) and p,p′-methoxychlor (MXC), in the coral tissues and mucus as well as in plankton and seawater from a coastal reef ecosystem (Weizhou Island) in the South China Sea. The results indicated that DDTs were the predominant OCPs in seawater and marine biota. Higher concentrations of OCPs in plankton may contribute to the enrichment of OCPs by corals. The significantly higher total OCP concentration (∑8OCPs) found in coral mucus than in coral tissues suggested that coral mucus played an essential role in resisting enrichment of OCPs by coral tissues. This study explored the different functions of coral tissues and mucus in OCP enrichment and biodegradation for the first time, highlighting the need for OCP toxicity experiments from both tissue and mucus perspectives.

Active acoustic telemetry reveals ontogenetic habitat-related variations in the coastal movement ecology of the white shark

BackgroundLittle is known about the fine-scale behavioural choices white sharks make. The assessment of movement at high spatio-temporal resolution can improve our understanding of behavioural patterns. Active acoustic telemetry was used along a coastal seascape of South Africa to investigate the movement-patterns of 19 white sharks tracked for 877 h within habitats known to host different prey types.ResultsA three-state hidden Markov model showed higher ontogenetic variability in the movements of white sharks around estuary-related coastal reef systems compared to around a pinniped colony. Our results further suggest white sharks (1) use the same searching strategy in areas where either pinnipeds or fishes are present; (2) occupy sub-tidal reef habitats possibly for either conserving energy or recovering energy spent hunting, and (3) travel directly between the other two states.ConclusionsWhite sharks appear not to simply roam coastal habitats, but rather adopt specific temporally optimized behaviours associated with distinct habitat features. The related behaviours are likely the result of a balance among ontogenetic experience, trophic niche, and energetics, aimed at maximizing the use of temporally and spatially heterogeneous environments and resources. The possible implications for the future conservation of white sharks in coastal areas are discussed, with particular attention to South Africa’s present conservation and management challenges.

Ecological indices from environmental DNA to contrast coastal reefs under different anthropogenic pressures

AbstractHuman activities can degrade the quality of coral reefs and cause a decline in fish species richness and functional diversity and an erosion of the ecosystem services provided. Environmental DNA metabarcoding (eDNA) has been proposed as an alternative to Underwater Visual Census (UVC) to offer more rapid assessment of marine biodiversity to meet management demands for ecosystem health indices. Taxonomic information derived from sequenced eDNA can be combined with functional traits and phylogenetic positions to generate a variety of ecological indices describing ecosystem functioning. Here, we inventoried reef fish assemblages of two contrasting coastal areas of Curaçao, (i) near the island's capital city and (ii) in a remote area under more limited anthropogenic pressure. We sampled eDNA by filtering large volumes of seawater (2 × 30 L) along 2 km boat transects, which we coupled with species ecological properties related to habitat use, trophic level, and body size to investigate the difference in fish taxonomic composition, functional and phylogenetic indices recovered from eDNA metabarcoding between these two distinct coastal areas. Despite no marked difference in species richness, we found a higher phylogenetic diversity in proximity to the city, but a higher functional diversity on the more isolated reef. Composition differences between coastal areas were associated with different frequencies of reef fish families. Because of a partial reference database, eDNA only partly matched those detected with UVC, but eDNA surveys nevertheless provided rapid and robust species occurrence responses to contrasting environments. eDNA metabarcoding coupled with functional and phylogenetic diversity assessment can serve the management of coastal habitats under increasing threat from global changes.

An experimental study on ghost fishing in rocky coastal reefs in southern Brazil

A ghost fishing experiment was conducted using gillnets in a rocky reef off the state of Santa Catarina, southern Brazil. Scuba divers monitored changes in the structure of the nets and catches for 92 days. One hundred and twenty-six entangled animals were observed, including target and non-target fishing species: 13 teleosts (N = 52; 43%) and four crustaceans (N = 74; 57%). The crab Menippe nodifrons was the most frequently entangled species (N = 36; 28%). Entanglement rates decreased over time following a logarithmic model for fishes and crustaceans, and an exponential model for both taxa combined, attributed to the degradation, and tangling of the nets and biofouling. The area of the net decreased linearly over time, collapsing after 92 days. This study provides the first experimental evaluation of the impacts of ghost fishing caused by gillnets in Brazilian rocky reefs.

Sailing into the past: Nautical charts reveal changes over 160 years in the largest reef complex in the South Atlantic Ocean

Coral reefs are in global decline due to unprecedented anthropogenic threats that have escalated and accumulated over decades to centuries. In order to assess the magnitude and drivers of changes on reefs, it is necessary to reconstruct the history of changes of these ecosystems over this longer time scale. We compiled and assessed historical records of naturalists that visited Abrolhos reefs over the last 202 years, and compared a 160-year-old nautical chart with modern charts to quantify losses in the spatial extent of coastal reefs in the Abrolhos Bank, Brazil. We found a 28% loss in the overall spatial extent of inshore reefs, with some areas experiencing declines up to 49% over the past 160 years. Such reefs with more dramatic changes (Guaratibas reefs) are the closest to the coast (∼7 km), where local impacts such as the past extraction of coral for lime since the 19th century, as well as increased coastal sedimentation and siltation due to deforestation are concentrated and that, combined, may have caused the observed decline. Collectively, this set of historical information captures coral reef changes over time, and helps update conservation and restoration goals for the Abrolhos reefs seascape.

Habitat and Marine Reserve Status Drive Reef Fish Biomass and Functional Diversity in the Largest South Atlantic Coral Reef System (Abrolhos, Brazil)

The effects of fishing have been documented across coral reefs worldwide. No-take marine reserves do not only act as a conservation tool but also allow an opportunity to study impacts of fishing, by acting as control sites. In addition, well-planned and well-managed no-take marine reserves (NTRs) provide conservation benefits that are essential to marine biodiversity and ecosystem-based management. The Abrolhos Marine National Park, off the tropical Brazilian coast, protects part of the largest coral reef system in the South Atlantic. To investigate the effects of fishing on reef fish richness, abundance, biomass, and functional diversity of the fish assemblage, we compared sites across two protection levels considering the variation in habitats (Fringing Reefs—Protected; Pinnacles Reefs—Protected; and Coastal Reefs—Open Access), using Baited Remote Underwater Stereo-Video systems (stereo-BRUVs). We adjusted generalized additive mixed models of fish assemblage characteristics with protection levels and environmental variables, such as topographic complexity (mean relief and relief variation), visibility, and benthic cover percentage. Inside NTRs, we found higher total biomass and biomass of fishery target species and carnivores, specifically for the Carcharhinidae (sharks) and Epinephelidae (groupers) families, indicating direct fisheries effects on these groups. In contrast, the ecological parameters of non-target fish were positively correlated with habitat characteristics, including mean relief and variance of relief. Moreover, fish functional diversity was higher within NTRs, demonstrating an even distribution of functional entities. The presence of large mobile predators and the overall higher biomass of carnivores inside the NTR indicate the effect of fishing exclusion. Our results point to the value of NTRs to study the effects of fishing and achieve biodiversity conservation and suggest the importance of using remote sampling methods to assess large mobile predators.

A highly diverse phytobenthic community along a short coastal reef gradient in northeastern Brazil

This study aimed to inventory the species of marine macroalgae and analyze the distribution and biomass patterns of their communities along a short coastal reef gradient in northeastern Brazil. Samples were collected using the technique of random squares, distributed in the three habitats: reef front region (FR), tide pools (TP), and reef plateau (RP). These three make up the reef gradient from the sea to the beach. A total of 56 taxa were identified, with Ochrophyta and Rhodophyta standing out as the phyla with the greater taxonomic richness, and the largest biomass represented by the species Sargassum vulgare (30 % of total biomass) and (16 %). The key emergening patterns along the reef gradient were the occurrence of groups of exclusive taxa in each habitat, and significant variation in biomass, greater in the TP (166.1 g m-2) and lower in the RP (70.5 g m-2). Despite being an environment under marked anthropogenic influence (i.e., tourism and development), we observed a high diversity of species, with a distribution pattern that reflects a high environmental heterogeneity and substantial ecological integrity.

Characterization of the mitochondrial genome of parupeneus indicus (perciformes, mullidae)

Parupeneus indicus, a species in the family Mullidae, inhabits the coastal and inner lagoon reefs of the Indian and Pacific oceans. The mitochondrial genome of P. indicus is 16,566 base pairs in length and contains 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes, and a D-loop control region. The overall base composition is 26.58% A, 24.83% T, 30.39% C, and 18.19% G, indicating an AT-rich profile (51.41%). Phylogenetic analysis based on the 13 PCGs revealed a close evolutionary relationship between P. indicus and P. barberinus. The data obtained in this study represent a valuable mitogenomic resource for population studies in the family Mullidae and will contribute to gaining a better understanding of the conservation genetics and environmental DNA of these fish.

Fish chorus and vessel noise in a marine protected coastal reef vary with lunar phase

Fish chorus and vessel noise in a marine protected coastal reef vary with lunar phase

Coral reef & temperate coastal soundscape features evident in directional and omnidirectional passive acoustic time series

Biologically complex coastal environments, such as coral reefs, demonstrate an equally rich ambient soundscape. Bioacoustic features of coastal soundscapes are closely tied with relative ecosystem health, functional groups present, and can be linked with specific behaviors. Biological contributions to ambient soundscapes have distinctive qualities as compared to sound associated with physical processes (i.e. wind and wave noise). While some biological components are readily identifiable, such as marine mammal or fish calls, the background noise associated with hundreds of thousands of biological clicks, snaps, and pops is not as well studied but contains a wealth of information about the ecosystem. A 64-element line array with 4.5 kHz design frequency was deployed for several field experiments off the coast of Kona, Hawaii in 2019 and 2020. Soundscape data from Hawaii were compared with comparable omnidirectional time series from Bermuda (2020) and coastal New England rocky reefs (2020–2021). Similarities in certain spectral features associated with biological sound sources were found between these unique ecosystems. The characteristic coral reef evening chorus, or significant increase in sound levels immediately prior to sunset, was consistent in Hawaii and Bermuda with comparable crepuscular changes in coastal New England.

Community size structure varies with predator-prey size relationships and temperature across Australian reefs.

Climate change and fisheries exploitation are dramatically changing the abundances, species composition, and size spectra of fish communities. We explore whether variation in ‘abundance size spectra’, a widely studied ecosystem feature, is influenced by a parameter theorized to govern the shape of size‐structured ecosystems—the relationship between the sizes of predators and their prey (predator–prey mass ratios, or PPMRs). PPMR estimates are lacking for avast number of fish species, including at the scale of trophic guilds. Using measurements of 8128 prey items in gut contents of 97 reef fish species, we established predator–prey mass ratios (PPMRs) for four major trophic guilds (piscivores, invertivores, planktivores, and herbivores) using linear mixed effects models. To assess the theoretical predictions that higher community‐level PPMRs leads to shallower size spectrum slopes, we compared observations of both ecosystem metrics for ~15,000 coastal reef sites distributed around Australia. PPMRs of individual fishes were remarkably high (median ~71,000), with significant variation between different trophic guilds (~890 for piscivores; ~83,000 for planktivores), and ~8700 for whole communities. Community‐level PPMRs were positively related to size spectrum slopes, broadly consistent with theory, however, this pattern was also influenced by the latitudinal temperature gradient. Tropical reefs showed a stronger relationship between community‐level PPMRs and community size spectrum slopes than temperate reefs. The extent that these patterns apply outside Australia and consequences for community structure and dynamics are key areas for future investigation.