Coral Patch Reefs Research Articles

Temporal shifts in algal and fish assemblages following the introduction of herbivorous species in coral reef patches (Bora Bora Island)

Ecological succession (sequential replacement of species following a disruptive event) is critical for understanding ecosystem dynamics. With coral reefs facing increasing threats, comprehending secondary ecological succession is of heightened importance. Coral reef restoration, through techniques such as coral transplantation and herbivore introduction, plays a crucial role in mitigating coral degradation at the local scale. However, the combined effect of these two techniques on ecological succession remains understudied. To determine the impact of herbivory and coral transplantation on ecological succession, four experimental conditions were evaluated on reef patches (Bora Bora, French Polynesia): (i) no-restored control, (ii) restored control, and two conditions with herbivorous invertebrates introduced (sea-urchins and mollusks) alongside restoration: (iii) one site with macroalgae removal and (iv) one without. Macroalgae cover and fish were monitored among the conditions over a 70-day period. Herbivorous invertebrates limited algae cover compared to control. However, no difference in fish assemblages was found in alpha diversity when comparing conditions over time. Changes in fish assemblages were observed in beta diversity, with statistically supported values for juveniles in the restored condition with herbivorous invertebrates present. Understanding the dynamics of ecological succession in so complex environments like coral reefs is essential for designing effective restoration strategies and safeguarding their health.

Displaced juvenile and subadult Caribbean spiny lobsters show strong orientation toward home dens

Caribbean spiny lobsters are known to undergo migration as adults, but the dispersal and homing ability of subadults and juveniles is not well characterized. Given that settlement habitat for juveniles is inshore seagrass / hardbottom and reproductive habitat is offshore coral reefs, dispersal during ontogeny serves as a bottleneck potentially limiting adult population density. Previous studies have examined factors associated with movement and den selection by juvenile lobsters such as shelter type, predators, and conspecific density. Their attraction to odors of healthy conspecifics plays a significant role in aggregation of lobsters in casitas and traps. But what is unknown is whether juvenile lobsters possess the map and compass orientation found in adults. To examine the ontogeny of homing ability, we conducted multiple mark / displace tracking studies using acoustic telemetry in juvenile hardbottom and subadult coral patch reef habitats. All lobsters regardless of size tend to relocate to new crevice shelters when handled, even if returned to their original shelter. Thus, for non-displaced lobsters tagged and returned to their point of capture, distance and angle travelled appears to be random with distance increasing as function of body size. However, for juvenile and subadult lobsters tagged and displaced away from their point of capture, the distance and angle travelled when released is significantly directed toward the point of capture. Thus, it appears that the map and compass ability of Caribbean spiny lobsters appears early in ontogeny and may allow for individuals to safely explore unfamiliar locations while retaining knowledge of how to return to known shelter. This ability to expand their known habitat map while maintaining knowledge of critical diurnal shelter locations is expected to facilitate their ontogenetic dispersal to adult habitat.

Testing sea urchin and green sea turtle consumption of the allelopathic macroalga Galaxaura divaricata.

Galaxaura divaricata is a partially calcified macroalga that hampers coral recruitment, growth, and recovery via the excretion of allelopathic secondary metabolites. Herbivorous fishes are not major consumers of Galaxaura spp. and there is a need to understand feeding preferences for Galaxaura divaricata in other macroherbivores, like sea urchins and green sea turtles that could act as potential controlling agents. Under certain environmental conditions, G. divaricata can proliferate and overgrow degraded reefs for several years, as documented for several coral patch reefs in the lagoon of Dongsha Atoll, South China Sea. This study aimed to experimentally test the feeding preferences of five species of sea urchin and two individual green sea turtles, Chelonia mydas, for G. divaricata. Specifically, we quantified and compared the consumption rates of the allelopathic G. divaricata with Gracilaria edulis, a nonallelopathic, fleshy red alga, known to be highly favored by herbivores. Results showed that the five urchin species fed on both G. edulis and G. divaricata. However, urchins consumed 2-8 times less wet weight of G. divaricata (range 0.3-3.1 g urchin-1 24 h-1) compared to G. edulis (range 0.6-18 g urchin-1 24 h-1), suggesting that urchin grazing may exert some control on G. divaricata abundance but is likely ineffective for a large-scale removal of the alga. Further, both green sea turtles avoided G. divaricata and selectively fed on G. edulis. More experiments are needed to test the potential role of herbivores in controlling the overgrowth of coral competitive and allelopathic macroalgae, like Galaxaura on coral reefs.

Succession of the sessile benthic community at a coral reef restoration site.

Introduction: Ecosystem restoration facilitates ecological succession. When a coral reef experiences a disturbance, the community of sessile benthic organisms can follow a successional trajectory that favors the dominance of coral or a change of state to an ecosystem dominated by algae. 
 Objective: To better understand the impact of coral transplants on succession of the sessile benthic community, this study 
 Methods: To measure and monitor the coral cover (cm2) of Pocillopora spp., and the composition of the associated benthic community, experimental and control coral reef patches were established at the coral restoration site in Golfo Dulce, South Pacific Costa Rica. Thirty Pocillopora spp. colonies were attached to nails on the substrate in an experimental patch. The control coral patch contained nails with non-transplanted colonies. Both treatments were photographed monthly during a period of eight months. Changes in the coverage of coral and other sessile benthic organisms were measured from the images and compared over time between the experimental and control patches. 
 Results: The coral transplants experienced bleaching events in August through September 2019 and January through February 2020. The first bleaching event possibly due to sedimentation, and the second to high temperatures. By the end of the experiment, 83 % of the colonies had survived. The live colonies grew significantly following transplantation; > 67 % of their initial coverage area after eight months. In the experimental patch, the areas of Pocillopora spp., coralline crustose algae (CCA), and cyanobacteria increased while the area of algal turf decreased. The increase in coral coverage and CCA, and decrease in algal turf in the experimental patch could be due to herbivores attracted to transplants. The increase in cyanobacteria in the experimental patch could be the result of higher temperatures and may have been a factor in the death of colonies. 
 Conclusions: The transplantation of Pocillopora spp. colonies in Golfo Dulce changed the early successional trajectory of the sessile benthic community to favor the dominance of coral dominance in the experimental patch. These results may be useful in informing expectations for future restoration efforts.

A deep learning model for measuring coral reef halos globally from multispectral satellite imagery

Reef halos are rings of bare sand that surround coral reef patches. Halo formation is likely to be the indirectly result of interactions between relatively healthy predator and herbivore populations. To reduce the risk of predation, herbivores preferentially graze close to the safety of the reef, potentially affecting the presence and size of the halo. Reef halos are readily visible in remotely sensed imagery, and monitoring their presence and changes in size may therefore offer clues as to how predator and herbivore populations are faring. However, manually identifying and measuring halos is slow and limits the spatial and temporal scope of studies. There are currently no existing tools to automatically identify single reef halos and measure their size to speed up their identification and improve our ability to quantify their variability over space and time. Here we present a set of convolutional neural networks aimed at identifying and measuring reef halos from very high-resolution satellite imagery (i.e., ∼0.6 m spatial resolution). We show that deep learning algorithms can successfully detect and measure reef halos with a high degree of accuracy (F1 = 0.824), thereby enabling faster, more accurate spatio-temporal monitoring of halo size. This tool will aid in the global study of reef halos, and potentially coral reef ecosystem monitoring, by facilitating our discovery of the ecological dynamics underlying reef halo presence and variability.

Stories told by corals, algae, and sea-urchins in a Mesoamerican coral reef: degradation trumps succession.

Understanding the mechanisms that allow the permanence of coral reefs and the constancy of their characteristics is necessary to alleviate the effects of chronic environmental changes. After a disturbance, healthy coral reefs display trajectories that allow regaining coral cover and the establishment of framework building corals. Through a comparative approach, in a patch reef partially affected by a ship grounding, we analyzed the successional trajectories in affected and unaffected sectors. Fleshy algae (which do not promote the recruitment of corals) dominated the reef surface irrespective of the impact of the ship grounding incident. Acropora species had near-zero contributions to community structure, whereas non-framework building corals like Porites sp. had a slightly higher recruitment. Cover of coral and calcareous crustose algae decreased over time, and neither the latter nor adult coral colonies had any effect on the occurrence probabilities of small corals. Sea urchin (Diadema antillarum) densities were generally low, and thus unlikely to contribute to reverting algal dominance. The successional trajectories of the community in the impacted and non-impacted sectors of the coral patch reef agree with the inhibition successional model, leading to the development of a degraded state dominated by fleshy algae. It is probable that the stability and resilience of this degraded state are high due to the ability of fleshy algae to monopolize space, along with low coral recovery potential.

How artificial potential field algorithms can help to simulate trade-offs in movement behaviour of reef fishes

IntroductionSpace use patterns in fish result from the interactions between individual movement behaviour and characteristics of the environment. Herbivorous parrotfishes, for instance, are constrained by the availability of resources and different predation risks. The resulting spatial distribution of the fish population can strongly influence community composition and ecosystem resilience.MethodsIn a novel approach, we combine individual-based modelling (IBM) with an artificial potential field algorithm to realistically represent fish movements and the decision-making process. Potential field algorithms, which are popular methods in mobile robot path planning, efficiently generate the best paths for an entity to navigate through vector fields of repellent and attracting forces. In our model the repellent and attracting forces are predation risk and food availability, both implemented as separate grid-based vector fields. The coupling of individual fish bioenergetics with a navigation capacity provides a mechanistic basis to analyse how the habitat structure influences population dynamics and space utilization.ResultsModel results indicate that movement patterns and the resulting spatial distributions strongly depend on habitat fragmentation with the bioenergetic capacity to spawn and reproduce being particularly susceptible processes at the individual level. The resulting spatial distributions of the population are more irregularly distributed among coral reef patches the more the coral reef habitat becomes fragmented and reduced.DiscussionThis heterogeneity can have strong implications for the delivered ecosystem functioning, e.g., by concentrating or diluting the grazing effort. Our results also highlight the importance of incorporating individual foraging-path patterns and the spatial exploitation of microhabitats into marine spatial planning by considering the effects of fragmentation. The integration of potential fields into IBMs represents a promising strategy to advance our understanding of complex decision-making in animals by implementing a more realistic and dynamic decision-making process, in which each fish weighs different rewards and risks of the environment. This information may help to identify core areas and essential habitat patches and assist in effective marine spatial management.

Predicting coral metapopulation decline in a changing thermal environment

Thermal stress is expected to compromise the persistence of tropical corals throughout their biogeographic ranges, making many reefs inhospitable to corals by the end of the century. We integrated models of local predictions of thermal stress throughout the coming century, coral larval dispersal, and the persistence of a coral’s metapopulation(s) in the Caribbean to investigate broad trends in metapopulation fragmentation and decline. As coral reef patches become inhospitable throughout the next century, the metapopulation of Orbicella annularis is predicted to fragment, with sub-networks centered around highly connected patches and thermal refuges. Some of these are predicted to include the reefs of Colombia, Panama, Honduras, Guatemala, Belize, Southern and Northern Cuba, Haiti, and the Bahamas. Unknown coral population demographic parameters, such as lifetime egg production and stock-recruitment rates, limit the model’s predictions; however, a sensitivity analysis demonstrates that broadscale patterns of fragmentation and metapopulation collapse before the end of the century are consistent across a range of potential parameterizations. Despite dire predictions, the model highlights the potential value in protecting and restoring coral populations at strategic locations that are highly connected and/or influential to persistence. Coordinated conservation activities that support local resilience at low coral cover have the potential to stave off metapopulation collapse for decades, buying valuable time. Thermal refuges are linchpins of metapopulation persistence during moderate thermal stress, and targeted conservation or restoration that supports connectivity between these refuges by enhancing local population growth or sexual propagation may be critically important to species conservation on coral reefs.

Spatio-temporal variability of sea surface temperatures in the Red Sea and their implications on Saudi Arabia coral reefs

The Red Sea is a conspicuous water body that hosts important coral reef ecosystems. This semi-closed sea is exposed to warming either by climate change or by anthropogenic stressors. The desalination plants along the Red Sea coast of Saudi Arabia dispose tremendous effluents of hot water from cooling systems, which is expected to impact the neighboring coral reef patches. The main objectives of this study were to delineate the spatial variations and the temporal trends of sea surface temperatures (SST) in the Red Sea using geospatial analysis with focusing on water temperature anomalies adjacent to seawater desalination plants. Monthly sea surface temperatures data were acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua satellite for the period 2003-2019. Annual SST changes and decadal trends were obtained from interpolation analysis and robust statistical metrics, respectively. Results showed that the Red Sea has three distinguished temperature zones with the coldest at the north and the warmest at the south. In addition, global warming is remarkably apparent in the northern part of the Red Sea (0.8 °C/decade). About one third of the Saudi corals occur at the northern part, while the remaining coral patches settle in the middle and southern parts of relatively lower SST trends. However, some corals in the middle section of the Red Sea occur proximate to regions of abruptly high SST trends due to the discharge of hot waters from desalination plants, particularly south of Jeddah. The continuous human-induced heating by hot water disposal could be fatal to coral reef ecosystems nearby desalination plants.

Isolation promotes abundance and species richness of fishes recruiting to coral reef patches

Habitat area and fragmentation are recognised as important factors that influence population size, community structure and extinction risk. Abundance and species richness universally increase with habitat area. However, the effects of different aspects of habitat fragmentation, including variation in patch size, number and isolation are often not distinguished from each other or the overall effects of habitat amount. Here we experimentally tested predictions concerning the effects of isolation on abundance, species richness and community structure of coral reef fishes colonising patch reefs by constructing clusters of patches of the same number and size, but manipulating reef spacing. Hexagonal clusters of 7 experimental patch reefs (6 edge and 1 central) with 3 levels of isolation (1 m, 5 m, and 15 m spacing) were established at Kavieng, Papua New Guinea and colonisation was recorded after 6 weeks in 2014. We also deployed video cameras to test whether isolation affected the activity of transient predatory fishes. As predicted, isolation had a positive effect on both mean abundance and species richness at both the cluster and patch scale. The cumulative abundance and species richness exhibited linear increases in relation to habitat area within clusters (from 1 to 7 patch reefs), but the slope increased with the degree of isolation. There was some evidence that transient predators remained longer and were more successful when patches were close together, which may explain the lower abundance and richness of juvenile fish assemblages on more aggregated patch reefs. This study demonstrates that while habitat amount is fundamentally important, isolation has significant effects that will need to be distinguished from other aspects of fragmentation when examining the processes structuring reef fish communities.

Sedimentary facies and paleoenvironmental interpretation of the Oligocene larger-benthic-foraminifera-dominated Qom Formation in the northeastern margin of the Tethyan Seaway

The well-exposed outcrops of the Bujan, northern Abadeh, and Varkan stratigraphic sections of the Qom Formation in the Iranian part of the “northeastern margin” of the Tethyan Seaway were characterized by abundant biogenic components dominated by foraminifers, coralline red algae, and corals. The Qom Formation is Rupelian–Chattian in age in the study areas. Based on the field investigations, depositional textures, and dominant biogenic components, fifteen (carbonate and terrigenous) facies were identified. These facies can be grouped into four depositional environments: open marine, open lagoon, restricted lagoon, and continental braided streams. The marine facies were deposited on a ramp-type platform. The euphotic inner ramp was characterized mainly by imperforate foraminifera, with co-occurrence of some perforate taxa. These facies passed basinward into a mesophotic (middle) ramp with Neorotalia packstone (F5), coral, coralline algae, perforate foraminiferal packstone (F4), and coral patch reefs (F7). The deeper, oligophotic ramp facies were marly packstones with planktonic and hyaline benthic foraminifera, including large lepidocyclinids and nummulitids. The abundance of perforate foraminifera and the absence of facies indicating restricted lagoonal or intertidal settings suggest that the Varkan section was deposited mainly in open marine settings with normal salinity. The prevalence of larger benthic foraminiferal and red algal assemblages, together with the coral facies, indicates that carbonate production took place in tropical–subtropical waters.

Lithostratigraphy and biostratigraphy of the uppermost Cretaceous to lowermost Palaeogene shallow-marine succession: top of the Adriatic Carbonate Platform at the Likva Cove section (island of Brač, Croatia)

The Likva Cove section on the island of Brač (Croatia) represents a rare example within the Adriatic Carbonate Platform (AdCP) succession of the basal Palaeocene limestones overlying the uppermost Maastrichtian shallow-platform limestones with evidence of only a brief stratigraphic hiatus at the Cretaceous/Palaeogene (K/Pg) contact. Detailed study of the 50-m-thick section resulted in the description of eight lithofacies arranged into six lithostratigraphic units: (A) rudist limestones, (B) deposits with coral–stromatoporoid patch reefs, (C) bindstones, and (D) fine-grained limestones with benthic and rare planktonic foraminifera in the uppermost Maastrichtian (comprising microfossil assemblage biozones I and II), and (E) limestones with benthic foraminifera (mostly discorbids), ostracods and rare planktonic foraminifera, and (F) ostracod–discorbid limestones in the lowermost Palaeocene (representing microfossil assemblage biozone III).The K/Pg contact is constrained between the last occurrence of Maastrichtian benthic and rare planktonic foraminifera, and the first occurrence of Danian planktonic and benthic foraminifera. The uppermost Cretaceous bed represents a firmground, but low biostratigraphic resolution precludes defining duration of a probable short-lasting hiatus at the K/Pg contact. Planktonic foraminifera are mixed with benthic forms in a 3.5-m-thick interval comprising the K/Pg contact as a consequence of decreased depositional rate and probable storm influence.Top of the section contains well developed coral patch reefs intensely karstified during a long-lasting regional unconformity, which in the studied part of the AdCP commenced in the early Palaeocene, i.e. later than at most parts of the platform. Therefore, the end of AdCP deposition should be locally extended into the Palaeocene in both its NW and SE parts.

Testing glacial isostatic adjustment models of last-interglacial sea level history in the Bahamas and Bermuda

Part of the spatial variation in the apparent sea-level record of the last interglacial (LIG) period is due to the diverse response of coastlines to glacial isostatic adjustment (GIA) processes, particularly where coastlines were close to the Laurentide Ice Sheet during the past two glacial periods. We tested modeled LIG paleo-sea levels on New Providence Island (NPI), Bahamas and Bermuda by investigating emergent coral patch reefs and oolitic/peloidal beach deposits. Corals with closed-system histories collected from patch reefs on NPI have ages of 128-118 ka and ooids/peloids from beach ridges have closed-system ages of 128-116 ka. Elevations of patch reefs indicate a LIG paleo-sea level of at least ∼7 m to ∼9 m above present. Beach ridge sediments indicate paleo-sea levels of ∼5 m to ∼14 m (assuming subsidence, ∼7 m to ∼16 m) above present during the LIG. Some, though not all of these measurements are in good agreement with GIA models of paleo-sea level that have been simulated for the Bahamas. On Bermuda, corals with closed-system histories collected from marine deposits have ages of 126-114 ka. Although coral-bearing marine deposits on Bermuda lack the precise indication of paleo-sea level provided by patch reefs and oolitic beach ridges, these sediments nevertheless provide at least a first-order estimate of paleo-sea level. Paleo-sea level records on Bermuda are consistently lower (∼2 m to ∼7 m) than what GIA models simulate for the LIG. The reason for the reasonable agreement with models for the Bahamas and poor agreement for Bermuda is not understood, but needs further investigation in light of the probability of a higher sea level in the near future.

Sedimentary facies and depositional environments of the Oligocene–early Miocene marine Qom Formation, Central Iran Back-Arc Basin, Iran (northeastern margin of the Tethyan Seaway)

The Qom Formation was deposited at the northeastern margin of the Tethyan Seaway. To analyze the sedimentary facies and depositional environments, the marine Qom Formation deposits in the Qom-Natanz region (Central Iran Back-Arc Basin) were studied. The Qom Formation is the main reservoir and source rock of hydrocarbons in central Iran. Studying the Qom Formation in Khurabad (SE Qom) and Natanz sections revealed that the study sections are dominated mainly by larger benthic foraminifera, coralline red algae, and corals. The Qom Formation is “Rupelian–Burdigalian” and “Rupelian?–Aquitanian” in age in the Khurabad and Natanz sections, respectively. Based on component distributions, texture, and field investigations, 14 different facies were identified and interpreted. A homoclinal ramp is the suggested model for the deposition of the Qom Formation in the study sections. Accordingly, open marine (middle ramp), lagoon (inner ramp), and peritidal flat/beach as major depositional environments were identified. The middle ramp was characterized by the association of perforate foraminifera, coralline red algae, bryozoans, echinoids, as well as planktonic foraminifera. The distal part of the inner ramp was characterized mainly by the co-occurrence of perforate and imperforate foraminifera. Coral patch reefs were also present, but there is no reef complex with sigmoidal geometries. The proximal part of the inner ramp was characterized mainly by imperforate foraminifera with low diversity. The terrigenous facies were more probably deposited in the high-stressed shoreface to the shallow inner ramp. However, the evaporative facies were deposited in a saltern environment. The abundant presence of larger benthic foraminifera (perforate and imperforate) and coralline red algae, as well as the presence of z-corals, emphasize a tropical–subtropical palaeoenvironment.

Multi-Trophic Species Interactions Shape Seascape-Scale Coral Reef Vegetation Patterns

How species interactions shape habitat structure is a longstanding question in ecology. A curious phenomenon reflecting ecological self-organization around reef habitat structures exists on coral reefs: large-scale (hundreds to hundreds of thousands of m2) halo-like patterns surrounding patch reefs, i.e., individual coral reefs that are often separated by seagrass or macroalgal meadows. These “halos,” long known to occur in various locations worldwide, reflect a distinct band of unvegetated sediments surrounding coral patch reefs. However, the full suite of mechanisms controlling them have never been rigorously explored, perhaps due to the common assumption dating back nearly 50 years that they arise solely from reef-based herbivory patterns shaped by anti-predator behavior. Here we provide empirical evidence from a set of halos within Australia's Great Barrier Reef that risk-averse foraging and a previously unrecognized functional group contribute to halo formation, demonstrating that these halos cannot be explained by any one mechanism in isolation. Our results show that halos are a more complex ecological phenomenon than previously assumed by the majority of studies of halos. Specifically, risk-averse grazing by herbivores is likely a key mechanism behind the formation of halos, as generally assumed, but bioturbators also play a central role. This knowledge furthers our understanding of how small-scale species interactions can structure habitat at landscape scales. These large-scale habitat features are important because they affect at least one important ecosystem function, carbon storage, and potentially others (e.g., biological nutrient transfer). These results also raise the question of whether other self-organized ecological patterns may be more nuanced than is currently assumed. This study capitalizes on recent advances in high resolution satellite imagery accessibility that allow ecologists to measure landscape-scale habitat features nearly everywhere on land and in shallow seas. Our results suggest that halos may hold potential as the basis for a tool for remotely observing ecological interactions and measuring large-scale ecosystem change on coral reefs.

In-situ incubation of a coral patch for community-scale assessment of metabolic and chemical processes on a reef slope.

Anthropogenic pressures threaten the health of coral reefs globally. Some of these pressures directly affect coral functioning, while others are indirect, for example by promoting the capacity of bioeroders to dissolve coral aragonite. To assess the coral reef status, it is necessary to validate community-scale measurements of metabolic and geochemical processes in the field, by determining fluxes from enclosed coral reef patches. Here, we investigate diurnal trends of carbonate chemistry, dissolved organic carbon, oxygen, and nutrients on a 20 m deep coral reef patch offshore from the island of Saba, Dutch Caribbean by means of tent incubations. The obtained trends are related to benthic carbon fluxes by quantifying net community calcification (NCC) and net community production (NCP). The relatively strong currents and swell-induced near-bottom surge at this location caused minor seawater exchange between the incubated reef and ambient water. Employing a compensating interpretive model, the exchange is used to our advantage as it maintains reasonably ventilated conditions, which conceivably prevents metabolic arrest during incubation periods of multiple hours. No diurnal trends in carbonate chemistry were detected and all net diurnal rates of production were strongly skewed towards respiration suggesting net heterotrophy in all incubations. The NCC inferred from our incubations ranges from −0.2 to 1.4 mmol CaCO3 m−2 h−1 (−0.2 to 1.2 kg CaCO3 m−2 year−1) and NCP varies from −9 to −21.7 mmol m−2 h−1 (net respiration). When comparing to the consensus-based ReefBudget approach, the estimated NCC rate for the incubated full planar area (0.36 kg CaCO3 m−2 year−1) was lower, but still within range of the different NCC inferred from our incubations. Field trials indicate that the tent-based incubation as presented here, coupled with an appropriate interpretive model, is an effective tool to investigate, in situ, the state of coral reef patches even when located in a relatively hydrodynamic environment.

Occurrence of microplastics in fishes from two landing sites in Tuticorin, South east coast of India

Microplastics pollution of the marine environment has been reported worldwide. Here, we investigate the occurrence of microplastics in two species of fishes namely Rastrilleger kanagurta and Epinephalus merra bought from Thirespuram and Punnakayal fish landing sites at Tuticorin. Out of the total 40 fish, 12 fish showed the presence of microplastic particulates in the intestine. The particulates included microfibers (80%) in red, black and translucent colors and irregularly shaped microplastic fragments (20%). The microplastics were identified as Polyethylene and Polypropylene by Fourier Transform Infrared Radiation analysis. Though microplastics were detected in the gut of the species, the risk of transfer due to consumption can be safely ruled out as the fish are degutted prior to consumption here. Presence of microplastics in the Tuticorin coast is a matter of concern due to its proximity to the Gulf of Mannar, a sensitive coral reef patch already threatened by marine pollution.

Fish movement drives spatial and temporal patterns of nutrient provisioning on coral reef patches

AbstractNutrient provisioning by animals can be a major driver of primary productivity in ecosystems. Animal‐mediated nutrient sources are particularly important in nutrient‐poor systems such as coral reefs. However, aggregations of mobile animals might lead to temporal and spatial variability in local nutrient availability, which is not well understood. In this study, we quantified how patterns of fish movement and abundance influence the stability of nitrogen provisioning on Bahamian coral reefs. We empirically measured and modeled nitrogen excretion estimates for 16 coral reef fish communities and combined these measurements with fish abundance and behavioral observations to compare reef nutrient budgets on diel, monthly, and annual time scales. Diel reef nitrogen provisioning by fishes varied greatly, with diurnal rates being on average four times greater than nocturnal rates. Diurnal rates were highly variable among reefs and were driven primarily by migratory grunts (Haemulidae) resting over reefs during the day but foraging off reefs at night. At the reef scale, overall nitrogen excretion rates were correlated with grunt abundance; however, grunt abundance could not be predicted by any reef physical characteristics. Within‐reef grunt excretion rates changed little across a 4‐month period but varied significantly over two years, indicating that nutrient supply on a patch reef is not stable over long periods of time. Quantifying how nutrient provisioning on patch reefs is linked to fish activity and movement patterns and how provisioning varies on different spatial and temporal scales is important for understanding overall patterns of primary productivity on reefs.

Coastal dynamics of uplifted and emerged late Pleistocene near-shore coral patch reefs at fins (eastern coastal Oman, Gulf of Oman)

We investigated two coral patch reefs of probably Weichselian age (Wyns et al., 1992a) which have been uplifted above sea-level in the coastal setting of uplifted marine terraces adjacent to the Oman Mountains. Uplift is also manifested in raised beach conglomerates and a wave-cut notch. We document some of the main reef features in the apprehension that building/development will preclude the study of the reefs in the near future. The reefs formed above a hardground of bioclastic limestone (mudstone to wackestone), characterized by intense bioerosion and red algae. The red algae may occur so plentiful to form (very localized) bafflestones. The diagenetic history of the rocks includes a transition from a marine environment (first cement) to meteoric conditions (dissolution and second cement). The reefs are 1.5 m thick and display planar as well as gently ocean-dipping reef tops, suggesting exposure to the wave-cut activity and, thus, shallow and nearshore deposition. The reefs are dominated by one coral species, identified as Cyphastrea serailia. On the protected side of the reefs the corals developed wavy and columnar growth forms while on the ocean facing side irregularly shaped exoskeletons developed. Our GPS-based topographic survey revealed an elevation of the two reefs of 21.5 m ± 0.06 m above sea-level. Taking into account (1) the global Holocene sea-level rise of 120 m ± 20 m (Pirazzoli and Pluet, 1991), (2) formation of the reefs slightly below sea-level (∼1.5 m) as well as (3) their present position above sea-level, we quantify the total upward transfer of the reefs to be 143 m and the average uplift rate to be 6.8 or 4.6 mm/yr depending on the correct age (either ∼21,000 or ∼31,000 yr B.P.). As the causes of uplift we mainly consider isostatic rebound following the late Cretaceous formation of the Oman Mountains (Yuan et al., 2016). The terrace development went through the following stages: (1) The patch reefs formed in shallow water. (2) Initial, gentle uplift caused abrasion of the reef tops. (3) Uplift continued and beach conglomerate 1was deposited on top of the reefs. (4) Abrasion continued, creating an abrasion platform. Uplift and creation of borings in platform required time and an interval of relatively slow uplift and tectonically and climatically stable conditions. (5) Uplift took place, and a wave-cut notch formed below the reefs. (6) Notch formation, including the borings into the notch, required time and stable conditions and was followed by deposition of beach conglomerate 2. (7) Finally, emergence/exposure of the notch and conglomerate 2 above sea-level ensued due to pronounced uplift, possibly associated with faulting and earthquakes. Formation of the reefs and the abrasion platform can be correlated with MIS 3 (Marine Isotope Stage 3) and notch formation with MIS 1.

Platy corals from the Middle Triassic of Upper Silesia, Poland: Implications for photosymbiosis in the first scleractinians

Coral patch reefs from Middle Triassic (upper Pelsonian–lower Illyrian) strata in the Upper Silesia region of southern Poland (Germanic domain of the Peri-Tethys) are rare examples of the first scleractinian buildups. The shallowing-upward succession in the Tarnów Opolski quarry records a transition from sponge to coral patch reefs interbedded with bioclastic limestones. Coral pillarstones built by thin, branching Volzeia szulci are succeeded by platy Pamiroseris silesiaca constructing two platestone layers, each up to 50cm thick. Serial sections through platestones revealed flat to undulose growth form of P. silesiaca. The maximum observable dimension of the coral plates is 24cm wide (typically up to 12cm), while thickness of most plates is 1–1.5cm. Coral plates are interlayered with crinoidal wacke- to packstone and microbialites, which are locally important component of the platestone. Platy corals grew in a shallow, turbid-water environment with changing, but dominantly moderate hydrodynamics. Net sedimentation was low, as indicated by the epibionts encrusted to the undersides of the coral plates, and locally common microbial fabrics. Growth-interruptions of P. silesiaca record events of storm-induced sediment input and resuspension of carbonate mud. Based on the euphotic floor model, the flattened morphology of P. silesiaca is interpreted as an optimal growth form in a turbid, low-light environment. Platy scleractinian assemblages from Silesia are the oldest occurrences of this ecological coral group (mostly representing deeper, mesophotic habitats) and support the hypothesis that some of the earliest scleractinians had photosymbionts like modern zooxanthellae.