Ecological Changes in the Coral Reef Communities of Indonesia's Bali Barat National Park, 2011–2016

Menjangan Island is located off the coast of NW Bali. The island and surrounding waters lie within a Marine Protected Area (MPA), as part of the Bali Barat National Park (BBNP), officially formed in 1984. Although many organizations have surveyed this reef area over the span of four decades, this is the first time that data on reef quality is compared over a nine year timeframe, from 2002 until 2011.From 19 March to 10 April 2011, eleven sites were studied: eight were located within Bali Barat National Park (BBNP) and three were located outside. The sites were clustered into areas identified as “BBNP Menjangan Is.” (sites surrounding Menjangan Island), “BBNP Sumber Klampok” (sites adjacent to the mainland) and “Sumber Kima” (sites outside the MPA). Sites within BBNP Menjangan Is. contained the highest mean cover of live hard corals (42%) although these sites also had the highest incidence of damaged coral colonies and of fishing gear. Comparisons of the benthic substrate data in 2011 with data collected in 2002 suggests that there was an overall increase in coral coverage in each of the 3 areas, as well as an increase in the damage to live hard corals. The two areas within BBNP had more than twice as much fish biomass in comparison with the area outside BBNP. Using the Index of Fish Diversity in the Indo Pacific region (CFDI; Allen and Werner, 2002), fish species were judged to be moderately diverse within the BBNP and poorly diverse outside. Although Menjangan Island lies within an MPA where no fishing is allowed, there is no enforcement of the no-take zone or prevention of anchoring by visitors to the island, and even as recently as July 2009 blast fishing was observed (pers. comm.). To help maintain the area as a reservoir for biodiversity as well as maintain the economic viability for the people of NW Bali, the Biosphere Foundation initiated a community-based conservation program called “Friends of Menjangan” with Yayasan Dwi Asih Sejahtera, a local Non-Governmental Organization (NGO). This community-based conservation movement is led by members of the local community, with approval from BBNP and participation by all stakeholders.

The status of reef fish density, diversity, species richness, biomass and coral cover was evaluated by comparing the conditions in two Dar es Salaam Marine Reserves (DMRs); the North Dar es Salaam Marine Reserve (NDMR; gazetted in 1975), and the South Dar es Salaam Marine Reserves (SDMRs; gazetted in 2007), before the 2016 El Niño. A 10 m line-intercept transect was used to characterize benthic cover and a 50 m belt transect was used to assess reef fish population status. Sampling occurred between August 2014 and April 2015. The results showed that fish biomass in the (NDMRs) was 2.7 times higher than that in the (SDMRs) and live hard coral cover was 3 times higher. Higher reef fish density, biomass, diversity, species richness and live hard coral cover were revealed before 2016 El Niño in NDMRs as compared to the SDMRs. Differences in status are linked to differences in time of gazetting and level of effective management in the marine protected areas (MPAs), where NDMRs has a General Management Plan (GMP) while SDMRs does not, and the differences in management are likely to have contributed to the differences in fish biomass and coral cover.

Coral reef ecosystems worldwide are under pressure from chronic and acute stressors that threaten their continued existence. Most obvious among changes to reefs is loss of hard coral cover, but a precise multi-scale estimate of coral cover dynamics for the Great Barrier Reef (GBR) is currently lacking. Monitoring data collected annually from fixed sites at 47 reefs across 1300 km of the GBR indicate that overall regional coral cover was stable (averaging 29% and ranging from 23% to 33% cover across years) with no net decline between 1995 and 2009. Subregional trends (10–100 km) in hard coral were diverse with some being very dynamic and others changing little. Coral cover increased in six subregions and decreased in seven subregions. Persistent decline of corals occurred in one subregion for hard coral and Acroporidae and in four subregions in non-Acroporidae families. Change in Acroporidae accounted for 68% of change in hard coral. Crown-of-thorns starfish (Acanthaster planci) outbreaks and storm damage were responsible for more coral loss during this period than either bleaching or disease despite two mass bleaching events and an increase in the incidence of coral disease. While the limited data for the GBR prior to the 1980's suggests that coral cover was higher than in our survey, we found no evidence of consistent, system-wide decline in coral cover since 1995. Instead, fluctuations in coral cover at subregional scales (10–100 km), driven mostly by changes in fast-growing Acroporidae, occurred as a result of localized disturbance events and subsequent recovery.

Near-shore marine environments are increasingly subjected to reduced water quality, and their ability to withstand it is critical to their persistence. The potential role marine reserves may play in mitigating the effects of reduced water quality has received little attention. We investigated the spatial and temporal variability in live coral and macro-algal cover and water quality during moderate and major flooding events of the Fitzroy River within the Keppel Bay region of the Great Barrier Reef Marine Park from 2007 to 2013. We used 7 years of remote sensing data on water quality and data from long-term monitoring of coral reefs to quantify exposure of coral reefs to flood plumes. We used a distance linear model to partition the contribution of abiotic and biotic factors, including zoning, as drivers of the observed changes in coral and macro-algae cover. Moderate flood plumes from 2007 to 2009 did not affect coral cover on reefs in the Keppel Islands, suggesting the reef has intrinsic resistance against short-term exposure to reduced water quality. However, from 2009 to 2013, live coral cover declined by ∼ 50% following several weeks of exposure to turbid, low salinity water from major flood plume events in 2011 and subsequent moderate events in 2012 and 2013. Although the flooding events in 2012 and 2013 were smaller than the flooding events between 2007 to 2009, the ability of the reefs to withstand these moderate floods was lost, as evidenced by a ∼ 20% decline in coral cover between 2011 to 2013. Although zoning (no-take reserve or fished) was identified a significant driver of coral cover, we recorded consistently lower coral cover on reserve reefs than on fished reefs throughout the study period and significantly lower cover in 2011. Our findings suggest that even reefs with an inherent resistance to reduced water quality are not able to withstand repeated disturbance events. The limitations of reserves in mitigating the effects of reduced water quality on near-shore coral reefs underscores the importance of integrated management approaches that combine effective land-based management with networks of no-take reserves.

Costa Rica es considerado uno de los 20 países del mundo con mayor biodiversidad, entre los que destacan sus ecosistemas arrecifales. Más precisamente, el Pacífico Sur, el Área de Conservación Osa, se ha considerado como una de las zonas más diversas en estos ecosistemas. Estos arrecifes han sido estudiados desde inicios de los años 80’s, pero enfocándose solamente en la cobertura coralinos de estos arrecifes. Por lo tanto, la presente investigación busca realizar una evaluación actualizada y con una metodología estándar él estado de varios componentes de los sistemas arrecifales de esta región. Entre el 2013 y el 2014, se visitaron cinco localidades: Dominicalito, Parque Nacional Marino Ballena, Reserva Biológica Isla del Caño, Península de Osa y Golfo Dulce, donde se evaluaron 27 sitios. En ellos se realizó la evaluación, a dos profundidades, de: cobertura del fondo, rugosidad del arrecife, diversidad y densidad de macroinvertebrados, así como la diversidad y biomasa de peces arrecifales. En términos generales los arrecifes de ACOSA, son moderadamente complejos y en ellos predominan el tapete algal (62.7%), mientras que la cobertura de coral vivo es moderada (16.5%). Se observó una diferencia entre la cobertura de tipos de sustratos por localidad, la cual puede estar atribuida a condiciones ambientales adversas (i.e. sedimentación, contaminación) para su desarrollo. Sin embargo, los arrecifes coralinos de Golfo Dulce e Isla del Caño muestran una notable recuperación al compararla con estudios previos. Se observaron 35 taxa de macroinvertebrados en los sitios estudiados, en su mayoría (58%) fueron poco abundantes u ocasionales. La mayor diversidad y densidad de macroinvertebrados se observó en Golfo Dulce y se determinaron diferencias significativas entre localidades. Este estudio brinda una línea base para muchos de estos organismos en varios de los sitios. Los equinoideos Diadema mexicanum y Eucidaris thouarsii fueron los organismos predominantes, y se reporta el cambute (Lobatus galeatus) en varios de los sitios de muestreo. De las 90 especies de peces, 10 fueron las de mayor ocurrencia y densidad. No hubo diferencias significativas en la diversidad y riqueza de especies de peces observadas entre localidades, pero si en la biomasa y en la composición de la comunidad íctica entre los sitios. Los sitios de la Isla del Caño fueron los más diversos de toda ACOSA, presentan biomasas importantes y de niveles tróficos altos. Mientras que Golfo Dulce difirió con respecto a las demás localidades. Según los resultados observados, los arrecifes de ACOSA presentan una alta biodiversidad. Las condiciones del de los ecosistemas indican que más esfuerzos de conservación, uso sostenible y manejo efectivo de loa recursos en tierra como en el mar deben ser implementados. El monitoreo ecológico va a proveer de la información sobre las tendencias y las relaciones entre el estado de los ecosistemas arrecifales y las condiciones ambientales.

Teluk Sebong is one of the areas around Bintan Island, Indonesia, that has potential coral reef resources. Bintan borders directly with neighbouring countries and with a major shipping lane (ALKI I) traversing the Indonesian Archipelago. This makes the coral reef ecosystems in this region particularly vulnerable to disruption from changes in the aquatic environment. There is a need for primary data on the coral reef ecosystem condition as a basis for understanding changes in this ecosystem. One commonly used method is the Coral Reef Health Index (CRHI), which can describe the current status in terms of live coral cover, the level of resilience (potential for recovery) during times of stress, the condition of economically important reef fish biomass, and ecologically related functions. The CRHI can be used in monitoring coral reef status and can provide a basis for the management of coral reef ecosystems. This study examined five sampling sites located in Teluk Sebong, Bintan Island. The in-situ data collection included the condition of coral reefs using the Underwater Photo Transect (UPT) method and reef fish condition using the Underwater Visual Census (UVC) method. The coral data collected were analyzed using the CPCe (Coral Point Calculate with Excel extension) software version 4.0 to determine the percentage benthic cover. The coral reef fish data were analyzed to provide target fish density and biomass values (carnivores and herbivores). The live coral cover in Teluk Sebong ranged from 30.87 - 45.40%. Out of the five research sites, Berakit, Pengudang, and Lagoi Bay had coral cover in the high category while coral cover at Banyan Tree and Rawa Island was in the medium category. Reef fish biomass in Teluk Sebong ranged from 9.26 - 108.07 kg/ha, and at all research sites fish biomass was in a low category. The coral reef ecosystem resilience in Teluk Sebong was high at the Berakit and Banyan tree sites; in contrast, Pengudang, Lagoi Bay, and Rawa Island were in the low resilience category. The coral reef index (CRHI) value was highest in Berakit (CRHI = 6), followed by Banyan Tree (CRHI = 5), Pengudang (CRHI = 4), Lagoi Bay (CRHI = 4), and Rawa Island (CRHI = 2).

BackgroundPredation pressure and herbivory exert cascading effects on coral reef health and stability. However, the extent of these cascading effects can vary considerably across space and time. This variability is likely a result of the complex interactions between coral reefs’ biotic and abiotic dimensions. A major biological component that has been poorly integrated into the reefs' trophic studies is the microbial community, despite its role in coral death and bleaching susceptibility. Viruses that infect bacteria can control microbial densities and may positively affect coral health by controlling microbialization. We hypothesize that viral predation of bacteria has analogous effects to the top-down pressure of macroorganisms on the trophic structure and reef health.ResultsHere, we investigated the relationships between live coral cover and viruses, bacteria, benthic algae, fish biomass, and water chemistry in 110 reefs spanning inhabited and uninhabited islands and atolls across the Pacific Ocean. Statistical learning showed that the abundance of turf algae, viruses, and bacteria, in that order, were the variables best predicting the variance in coral cover. While fish biomass was not a strong predictor of coral cover, the relationship between fish and corals became apparent when analyzed in the context of viral predation: high coral cover (> 50%) occurred on reefs with a combination of high predator fish biomass (sum of sharks and piscivores > 200 g m−2) and high virus-to-bacteria ratios (> 10), an indicator of viral predation pressure. However, these relationships were non-linear, with reefs at the higher and lower ends of the coral cover continuum displaying a narrow combination of abiotic and biotic variables, while reefs at intermediate coral cover showed a wider range of parameter combinations.ConclusionsThe results presented here support the hypothesis that viral predation of bacteria is associated with high coral cover and, thus, coral health and stability. We propose that combined predation pressures from fishes and viruses control energy fluxes, inhibiting the detrimental accumulation of ecosystem energy in the microbial food web.

Gradients of abundance and biomass across reserve boundaries in six Mediterranean marine protected areas: Evidence of fish spillover?

Coral reefs are undergoing changes caused by coastal development, resource use, and climate change. The extent and rate of reef change demand robust and spatially explicit monitoring to support management and conservation decision-making. We developed and demonstrated an airborne-assisted approach to design and upscale field surveys of reef fish over an ecologically complex reef ecosystem along Hawai‘i Island. We also determined the minimal set of mapped variables, mapped reef strata, and field survey sites needed to meet three goals: (i) increase field survey efficiency, (ii) reduce field sampling costs, and (iii) ensure field sampling is geostatistically robust for upscaling to regional estimates of reef fish composition. Variability in reef habitat was best described by a combination of water depth, live coral and macroalgal cover, fine-scale reef rugosity, reef curvature, and latitude as a proxy for a regional climate-ecosystem gradient. In combination, these factors yielded 18 distinct reef habitats, or strata, throughout the study region, which subsequently required 117 field survey sites to quantify fish diversity and biomass with minimal uncertainty. The distribution of field sites was proportional to stratum size and the variation in benthic habitat properties within each stratum. Upscaled maps of reef survey data indicated that fish diversity is spatially more uniform than fish biomass, which was lowest in embayments and near land-based access points. Decreasing the number of field sites from 117 to 45 and 75 sites for diversity and biomass, respectively, resulted in a manageable increase of statistical uncertainty, but would still yield actionable trend data over time for the 60 km reef study region on Hawai‘i Island. Our findings suggest that high-resolution benthic mapping can be combined with stratified-random field sampling to generate spatially explicit estimates of fish diversity and biomass. Future expansions of the methodology can also incorporate temporal shifts in benthic composition to drive continuously evolving fish monitoring for sampling and upscaling. Doing so reduces field-based labor and costs while increasing the geostatistical power and ecological representativeness of field work.

The world's coral reefs are being degraded, and the need to reduce local pressures to offset the effects of increasing global pressures is now widely recognized. This study investigates the spatial and temporal dynamics of coral cover, identifies the main drivers of coral mortality, and quantifies the rates of potential recovery of the Great Barrier Reef. Based on the world's most extensive time series data on reef condition (2,258 surveys of 214 reefs over 1985-2012), we show a major decline in coral cover from 28.0% to 13.8% (0.53% y(-1)), a loss of 50.7% of initial coral cover. Tropical cyclones, coral predation by crown-of-thorns starfish (COTS), and coral bleaching accounted for 48%, 42%, and 10% of the respective estimated losses, amounting to 3.38% y(-1) mortality rate. Importantly, the relatively pristine northern region showed no overall decline. The estimated rate of increase in coral cover in the absence of cyclones, COTS, and bleaching was 2.85% y(-1), demonstrating substantial capacity for recovery of reefs. In the absence of COTS, coral cover would increase at 0.89% y(-1), despite ongoing losses due to cyclones and bleaching. Thus, reducing COTS populations, by improving water quality and developing alternative control measures, could prevent further coral decline and improve the outlook for the Great Barrier Reef. Such strategies can, however, only be successful if climatic conditions are stabilized, as losses due to bleaching and cyclones will otherwise increase.

Many Caribbean reefs have experienced a phase-shift in community structure, the principle features being a decline in coral cover and an increase in macroalgal biomass. However, one Jamaican reef—Dairy Bull on the north shore near Discovery Bay—is once again dominated by scleractinian corals and several key species have returned. Living coral cover at 6–8 m depth at Dairy Bull has doubled over the past 9 years and is now ~54%. The absolute cover of Acropora cervicornis was <1% in 1995, but increased to ~11% by January 2004. During this time the cover of macroalgae decreased by 90%, from 45 to 6%. We speculate that long-lived colonies of Montastraea annularis may have facilitated the recovery of this reef by providing structural refugia.

An influential paradigm in coral reef ecology is that fishing causes trophic cascades through reef fish assemblages, resulting in reduced herbivory and thus benthic phase shifts from coral to algal dominance. Few long‐term field tests exist of how fishing affects the trophic structure of coral reef fish assemblages, and how such changes affect the benthos. Alternatively, benthic change itself may drive the trophic structure of reef fish assemblages. Reef fish trophic structure and benthic cover were quantified almost annually from 1983 to 2014 at two small Philippine islands (Apo, Sumilon). At each island a No‐Take Marine Reserve (NTMR) site and a site open to subsistence reef fishing were monitored. Thirteen trophic groups were identified. Large planktivores often accounted for >50% of assemblage biomass. Significant NTMR effects were detected at each island for total fish biomass, but for only 2 of 13 trophic components: generalist large predators and large planktivores. Fishing‐induced changes in biomass of these components had no effect on live hard coral (HC) cover. In contrast, HC cover affected biomass of 11 of 13 trophic components significantly. Positive associations with HC cover were detected for total fish biomass, generalist large predators, piscivores, obligate coral feeders, large planktivores, and small planktivores. Negative associations with HC cover were detected for large benthic foragers, detritivores, excavators, scrapers, and sand feeders. These associations of fish biomass to HC cover were most clear when environmental disturbances (e.g., coral bleaching, typhoons) reduced HC cover, often quickly (1–2 yr), and when HC recovered, often slowly (5–10 yr). As HC cover changed, the biomass of 11 trophic components of the fish assemblage changed. Benthic and fish assemblages were distinct at all sites from the outset, remaining so for 31 yr, despite differences in fishing pressure and disturbance history. HC cover alone explained ~30% of the variability in reef fish trophic structure, whereas fishing alone explained 24%. Furthermore, HC cover affected more trophic groups more strongly than fishing. Management of coral reefs must include measures to maintain coral reef habitats, not just measures to reduce fishing by NTMRs.

The crown-of-thorns starfish (COTS), Acanthaster cf. solaris, is one of the main contributors to declines in coral cover on the Great Barrier Reef (GBR) and remains one of the major acute disturbances on coral reefs throughout much of the Indo-Pacific. Extensive control programs on the GBR involve manual culling of COTS in the field, and research is needed to inform these management efforts. Data from the Great Barrier Reef Marine Park Authority’s (GBRMPA) COTS control program provide near-real-time CPUE (Catch-Per-Unit-Effort, COTS culled per minute) data ideal for operational decision-making but these must be converted to density estimates before they can be related to ecological status of reefs or incorporated into ecological models. We developed conversions between common COTS field survey methods (i.e. manta tow, SCUBA transect searches) and COTS control program CPUE data using estimates of sightability and detectability. We used a population model and COTS size-structure data from COTS control program culling efforts to estimate that, on average, only 19% of 1-yr-old COTS (1–15 cm) are available to be culled. Finally, we developed a CPUE-COTS density relationship to estimate the threshold levels of COTS that prevent net growth of hard corals. Culling programs should therefore aim to achieve CPUEs below these ecological thresholds in order to effectively promote coral growth and recovery. These ecologically sustainable thresholds of COTS density varied depending on hard coral cover. For example, for 35% fast-growing coral cover, COTS culling needs to continue until CPUE decreases to below 0.05 COTS/min (1 COTS per 20 min) in order to prevent coral decline, whereas if coral cover is higher (80%), then a higher target threshold CPUE of ca. 0.08 COTS/min (ca. 3 COTS per 40 min) may be ecologically sustainable. These estimates underpin the current pest management rules being implemented by the GBRMPA in its COTS control program.

The existence of coral reef fish is closely related to the availability of coral reef resource as a habitat. Coral reef fish is a biota that has a fascination with a variety of color patterns and fascinating. Differences in coral cover conditions will affect the abundance of coral reef fish, especially those with strong linkages to living corals. This research was conducted in June - August 2017 by using line intercept transect (LIT) method for coral cover percentage and visual census method for biodiversity and biomass of coral reef fish with 3 research stations in Manggis waters, Karangasem. From the research results, it shows that the diversity index ranged between 2.54 - 2.70 which means the diversity of coral reef fish in the medium category and the stability of the community is in the medium. Furthermore, total biomass of coral reef fish ranged between 186,17 - 1692,08 kg / ha. The results stated that the percentage of live coral cover in Manggis waters ranged from 3.83% to 12.44% which means that live coral cover is categorized as bad. A very strong positive correlation between living coral conditions and coral reef fish biomass was 92.42%. Meanwhile, the relationship between living coral conditions and the diversity of coral reef fish had a strong positive correlation of 65.4%. The diversity of coral reef fish in waters is not only caused by live coral cover; however, it is caused by coral reef ecosystems that are associated in the bottom of the waters.

From 1992 to 1997 changes in cover of hard and soft corals and macro-algae were monitored using annual video transect surveys on the northeast flank of up to 52 reefs along most of the Great Barrier Reef (GBR). Trends in cover of hard corals, algae and soft corals were usually consistent among clusters of adjacent or nearby reefs. This consistency probably reflected the spatial scales of the effect of episodic disturbances caused by cyclones or crown-of-thorns starfish Acanthaster planci. Hence, our comprehensive monitoring of a single habitat provided an effective indicator of the status and trends on adjacent reefs. Moreover, we observed broad-scale patterns of increase and decline in coral cover that suggest that a 'patchwork mosaic' null model is a useful concept at scales of whole reefs and regions. At a large spatial scale (up to 10° of latitude), cover of hard corals within the NE slope habitat averaged 29% (± 12.4 standard deviation) and increased by 1.7% (±6.5) over 5 yr of surveys. Cover of soft corals and algae remained constant and averaged 14% (±12.4) and 41% (±16.6) respectively. Inner shelf, mid-shelf and outer shelf reefs in a 'recovery' phase increased their cover of hard coral at average annual rates of 2.6% (±3.0), 3.9% (±4.1) and 4.3% (±4.5) respectively. Year-to-year changes in cover of soft corals were typically smaller and less variable than changes in cover of hard corals or algae. There was no evidence of any shift to alternative stable states of assemblage composition.