Urban Reefs Research Articles

Suva Urban Reefs: An ecological history of the coral reefs of the Greater Suva Urban Area, Fiji

Suva Urban Reefs: An ecological history of the coral reefs of the Greater Suva Urban Area, Fiji

Multi-indicator ‘state space’ approach to assessing changes in shallow urban reef ecosystem health

Tracking changes in ecosystem health is an important objective for environmental managers, but is often limited by an understanding of what constitutes a “healthy” system and how to aggregate a range of health indicators into a single meaningful metric. We used a multi-indicator ‘state space’ approach to quantify changes over 13 years in reef ecosystem health in an urban area that has undergone intense housing development. Based on nine health indicators (macroalgal canopy length and biomass, macroalgal canopy and habitat functional diversity, mobile and predatory invertebrate density and size, total species and non-indigenous species richness), we found that the overall health of the reef community declined at five of the ten study sites. This decline was associated with a large collapse in the gastropod community, a shortening of macroalgal canopies and an increase in the number of non-indigenous species. While the cause of this decline and mechanisms responsible are not fully understood, the decline correlated with an increase in sediment cover on the reefs and warming ocean temperatures over the monitoring period. The proposed approach provides an objective and multifaceted quantitative assessment of ecosystem health that can be easily interpreted and communicated. These methods could be adapted to other ecosystem types to inform management decisions regarding future monitoring, conservation and restoration priorities to achieve greater ecosystem health.

Translocation of intertidal corals in highly urbanized Mumbai seascape: A pragmatic management initiative towards ecosystem conservation

Coral reefs harbour rich biodiversity by increasing heterogeneous habitat and providing numerous ecosystem services and goods. However, they are highly threatened due to ongoing climate change and various anthropogenic activities. Therefore, the protection of corals is enforced by laws and legislative machinery around the globe. The present work is a case study in the highly urbanized Mumbai city, where a coastal road project required dredging and reclamation that overlapped with a coral habitat. A detailed environmental mitigation plan was undertaken to preserve the fragile corals at the proposed project site. A total of 329 colonies of Pseudosiderastrea tayamai Yabe & Sugiyama, 1935, were relocated from the project site to a recipient site after verifying the habitat suitability. Monthly coral health monitoring was conducted for one year after their relocation to the new habitat. After one year of translocation, 92.1% (n = 303) colonies survived and were in healthy state. Coral bleaching is a well-known phenomenon that occurs due to extreme variability in temperature, salinity and siltation etc. In the present study, coral bleaching was observed during monsoon (July – September 21) wherein maximum (94.83%) occurred in August 21 and minimum (4.86%) was in November 21. Algal overgrowth on coral colonies (maximum 38.9%), and sediment smothering (maximum 44.8%) were observed, but no colony mortality was noted (Jan – May 21). Whereas, 3.4% mortality was recorded during monsoon season only. The gross new recruitment (n = 22) of corals was also recorded collectively during the months of April, May and November 21. Therefore, the current study suggests that relocating corals from coastal development sites, where habitat loss is unavoidable, could be considered a tool that will aid in conservation of urban reefs. This study proves that only committed involvement of stakeholders and project proponents who have developmental perspective with environmental accountability can achieve the sustainability of rare and fragile ecosystems.

A community and functional comparison of coral and reef fish assemblages between four decades of coastal urbanisation and thermal stress.

Urbanized coral reefs experience anthropogenic disturbances caused by coastal development, pollution, and nutrient runoff, resulting in turbid, marginal conditions in which only certain species can persist. Mortality effects are exacerbated by increasingly regular thermal stress events, leading to shifts towards novel communities dominated by habitat generalists and species with low structural complexity.There is limited data on the turnover processes that occur due to this convergence of anthropogenic stressors, and how novel urban ecosystems are structured both at the community and functional levels. As such, it is unclear how they will respond to future disturbance events.Here, we examine the patterns of coral reef community change and determine whether ecosystem functions provided by specialist species are lost post‐disturbance. We present a comparison of community and functional trait‐based changes for scleractinian coral genera and reef fish species assemblages subject to coastal development, coastal modification, and mass bleaching between two time periods, 1975–1976 and 2018, in Nakagusuku Bay, Okinawa, Japan.We observed an increase in fish habitat generalists, a dominance shift from branching to massive/sub‐massive corals and increasing site‐based coral genera richness between years. Fish and coral communities significantly reassembled, but functional trait‐based multivariate space remained constant, indicating a turnover of species with similar traits. A compression of coral habitat occurred, with shallow (<5 m) and deep (>8 m) coral genera shifting towards the mid‐depths (5–8 m).We show that although reef species assemblages altered post disturbance, new communities retained similar ecosystem functions. This result could be linked to the stressors experienced by urban reefs, which reflect those that will occur at an increasing frequency globally in the near future. Yet, even after shifts to disturbed communities, these fully functioning reef systems may maintain high conservation value.

Differential Response of the Microbiome of Pocillopora acuta to Reciprocal Transplantation Within Singapore

As corals continue to decline globally, particularly due to climate change, it is vital to understand the extent to which their microbiome may confer an adaptive resilience against environmental stress. Corals that survive on the urban reefs of Singapore are ideal candidates to study the association of scleractinians with their microbiome, which in turn can inform reef conservation and management. In this study, we monitored differences in the microbiome of Pocillopora acuta colonies reciprocally transplanted between two reefs, Raffles and Kusu, within the Port of Singapore, where corals face intense anthropogenic impacts. Pocillopora acuta had previously been shown to host distinct microbial communities between these two reefs. Amplicon sequencing (16S rRNA) was used to assess the coral microbiomes at 1, 2, 4, and 10 days post-transplantation. Coral microbiomes responded rapidly to transplantation, becoming similar to those of the local corals at the destination reef within one day at Raffles and within two days at Kusu. Elevated nitrate concentrations were detected at Raffles for the duration of the study, potentially influencing the microbiome’s response to transplantation. The persistence of corals within the port of Singapore highlights the ability of corals to adapt to stressful environments. Further, coral resilience appears to coincide with a dynamic microbiome which can undergo shifts in composition without succumbing to dysbiosis.

Dataset of macrobenthic species in urban coastal reef environments in Brazilian northeast.

This dataset presents the macrobenthic species occurrence frequency in four coastal intertidal reefs environment of Paraiba state Brazil. The species were classified in bioindicators groups based in morpho-anatomical, physiological and ecological characteristics. In the dry and wet season in each reef, the sampling units were randomly positioned and photographed inside a circular area with a 10 m radius. Thirty points were plotted over photos to quantify the percentage of species occurrence frequency. Taxons hard to identify by photo were grouped in a unique category. Currently, macrobenthic species are used as bioindicators of the local state of conservation by managing agencies. The population ecology monitoring of macrobenthic species with bioindicator potential is useful to recognize seasonal environmental patterns or local anthropic impactful. The research article on these data [1] will be published in the journal Ocean and Coastal Management for some interpretive insights. Title: Evaluation of the conservation status and monitoring proposal for the coastal reefs of Paraíba, Brazil: bioindication as an environmental management tool.

Responses of urban reef corals during the 2016 mass bleaching event

Predicting the bleaching responses of corals is crucial in light of frequent heat stress events to manage further losses of biodiversity and ecosystem functioning, especially for reefs impacted by urbanisation. We examined if the coral cover and community at various Singapore sites changed during the 2016 global coral bleaching event. Bleaching prevalence varied widely among sites in June 2016, and was best explained by site and coral species. While some sites were minimally impacted, others registered significant decreases in coral cover and community changes persisting till March 2017, when normal colouration was mostly regained by corals. Bleaching susceptibility was associated with larger corallites in hermaphrodites and smaller corallites in gonochores (probably due to the cost of maintaining dual sexual functions in hermaphrodites), and with increasing proximity between polyps (likely because thermal damage would be less contained among polyps with greater physiological integration). However, bleaching resilience—the capacity to regain baseline pigmentation—was poorly explained by the traits studied. Our findings suggest that the interplay between local conditions and species composition strongly affects bleaching outcomes on urbanised reefs, and underscore the utility of coral traits for predicting bleaching responses to help in formulating appropriate management strategies.

The effects of a stressed inshore urban reef on coral recruitment in Suva Harbour, Fiji.

A relic inshore reef ecosystem adjacent to the Fijian capital of Suva and another remote inshore reef were monitored monthly from July 2014 to July 2015 for coral recruitment, sedimentation rates, coral cover, temperature, and light intensity. Despite a major sewage spill in Suva Harbour in December 2014, the municipal inshore site exposed to constant anthropogenic activity, recorded no significant differences in coral spat abundance (except for the family Poritidae) on artificial substrata compared to the remote inshore site. Total yearly spat abundance was 106 on municipal reef and 132 on remote reef, while average daily sediment trap collection rates (g cm2/day) were significantly higher in the municipal site for the entire duration of monitoring. Total annual particulate organic matter content in sediment was also significantly higher in the municipal site (107.51 g cm2), compared to the remote site (43.37 g cm2). Mean light intensity was significantly lower for the municipal site (69.81 lum/ft2) compared to the remote site (239.26 lum/ft2), with Photosynthetically Active Radiation also lower for the former (800–1,066.66 µmol m−2 s−1) compared to the latter (3,266.66–3,600 µmol m−2 s−1). The lack of significant differences in coral spat recruitment rates suggests that settling larvae may be unable to distinguish between sub‐optimal and optimal sites probably as a consequence of interference with coral settlement cues arising from anthropogenic development.

Genetic diversity and population structure of Siganus fuscescens across urban reefs of Seribu Islands, Northern of Jakarta, Indonesia

Bramandito A, Subhan B, Prartono T, Anggraini NP, Januar HI, Madduppa HH. 2018. Genetic diversity and population structure of Siganus fuscescens across urban reefs of Seribu Islands, Northern of Jakarta, Indonesia. Biodiversitas 19: 1993-2002. Jakarta bay and Seribu Islands reefs have been affected by anthropogenic activities which causing them degraded and low quality of the ecosystem. However, lack of study has been conducted to investigate the effect on reef fish population due to change in ecosystem quality. Therefore, this study was undertaken to analyze genetic diversity and population structure of Siganus fuscescens population against heavy metals (Pb, Cd, and Cu) concentration across Jakarta Bay and Seribu Islands environmental gradient. Genetic diversity and structuring of S. fuscescens populations were determined using partial sequences of the mitochondrial cytochrome C oxidase I. Monitoring of heavy metal was measured by Atomic Absorption Spectroscopy (AAS) shows highest concentration of heavy metal (Pb, Cd, and Cu) was observed in the southern of Seribu Islands, closest to Jakarta. However, the diversity of haplotype obtained from each location indicates a varied range between 0,1429 (Pramuka Island, located in the center) and 0,75 (Untung Jawa Island, located in the south). Linear regression test reveals that Cu elements had a moderate effect (R2 adjusted = 0.665) to the nucleotide diversity of the fish. The study shows some populations of S. fuscescens have been affected by heavy metal and could be an alarm to manage this artisanal targeted fish in the Seribu Islands.

Urban coral reefs: Degradation and resilience of hard coral assemblages in coastal cities of East and Southeast Asia

Given predicted increases in urbanization in tropical and subtropical regions, understanding the processes shaping urban coral reefs may be essential for anticipating future conservation challenges. We used a case study approach to identify unifying patterns of urban coral reefs and clarify the effects of urbanization on hard coral assemblages. Data were compiled from 11 cities throughout East and Southeast Asia, with particular focus on Singapore, Jakarta, Hong Kong, and Naha (Okinawa). Our review highlights several key characteristics of urban coral reefs, including “reef compression” (a decline in bathymetric range with increasing turbidity and decreasing water clarity over time and relative to shore), dominance by domed coral growth forms and low reef complexity, variable city-specific inshore-offshore gradients, early declines in coral cover with recent fluctuating periods of acute impacts and rapid recovery, and colonization of urban infrastructure by hard corals. We present hypotheses for urban reef community dynamics and discuss potential of ecological engineering for corals in urban areas.

Using citizen science data to assess the difference in marine debris loads on reefs in Queensland, Australia

The prevalence of marine debris in global oceans is negatively impacting the marine environment. In Australia, marine debris has been an increasing concern for sensitive marine environments, such as coral reefs. Citizen science can contribute data to explore patterns of subtidal marine debris loads. This study uses data from Reef Check Australia to describe patterns of debris abundance on reef tourism sites in two Queensland regions, the Great Barrier Reef (GBR) and Southeast Queensland (SEQ). Debris was categorized into three groups, fishing line, fishing net, and general rubbish. Overall, debris abundance across reefs was relatively low (average 0.5–3.3 items per survey (400 m2)), but not absent on remote reefs surveyed in the GBR region. Highest debris loads were recorded in SEQ near cities and high use areas. These results indicate the presence of marine debris on remote and urban reefs, and the applicability of using citizen science to monitor debris abundance.

Construyendo el arrecife urbano. (Ensayo, texto inédito), Feike de Jong

Construyendo el arrecife urbano. (Ensayo, texto inédito), Feike de Jong

Three new intertidal sponges (Porifera: Demospongiae) from Brazil’s fringing urban reefs (Maceió, Alagoas, Brazil), and support for Rhabderemia’s exclusion from Poecilosclerida

The inventory of Brazil’s marine sponge fauna is notably fragmentary; knowledge remains basic even in the vicinity of some important urban areas. Accordingly, we set up a plan to prioritize taxonomic study of sensitive areas, coupling high biodiversity potential and likely outstanding human pressure on biological resources. One such area comprises the fringing urban reefs of Maceió (Alagoas State, northeastern Brazil), from where three new demosponges are described here: Plakina coerulea sp. nov., Rhabderemia meirimensis sp. nov. and Mycale rubra sp. nov. The new Rhabderemia shares with Biemna, Desmacella, Neofibularia and Sigmaxinella, the possession of distally microspined sigmas. Recent molecular results have shown these taxa to be only distantly related to chelae-bearing Poecilosclerida, hence our decision to leave the new species as ordo incertae sedis. It is proposed that the intertidal or shallow subtidal sponge fauna in northeastern Brazil’s reefs deserves enhanced conservation effort to preserve what remains in these highly impacted ecosystems.http://www.zoobank.org/urn:lsid:zoobank.org:pub:4F150A0A-2371-40A1-B7B2-8CD14CEB885C

Can stormwater be detected by algae in an urban reef in Hawai‘i?

Nitrogen (N) enrichment of tropical reefs can result in the dominance of invasive algae. The invasive alga Acanthophora spicifera and the native alga Laurencia nidifica are part of a diverse reef assemblage in ‘Ewa Beach, O‘ahu. Their N contents and δ15N values were investigated to determine if N was enriched and to evaluate potential nitrogenous sources near and removed from storm-drain outlets. δ15N values of algae (3.8–17.7‰) were within and above the range for algae around the island (1.9–11.9‰). Elevated algae N isotope values (δ15N>+7‰, [N]>1.6%) and seawater nitrate+nitrite levels (0.59–7.93μM) indicated a mixed, high nutrient environment. The overlap in δ15N values with multiple nitrogenous sources precluded identification. However, spatial and temporal patterns did not support stormwater as the dominant, nitrogenous source. Patterns were congruent with algal incorporation of terrestrial derived N, subjected to a high degree of biogeochemical cycling.