Effect of species, size, and chimerism on the susceptibility of Caribbean brain coral recruits to stony coral tissue loss disease (SCTLD)

Stony coral tissue loss disease (SCTLD) has devastated coral populations along Florida′s Coral Reef and beyond. Although widespread infection and mortality of adult colonies have been documented, no studies have yet investigated the susceptibility of recruits to this disease. Here, we exposed eight-month-old Diploria labyrinthiformis recruits and four-month-old Colpophyllia natans recruits to two sequential doses of SCTLD in the laboratory to track infection and assess potential resilience. Both species began to develop lesions as early as 48 h after exposure began. During the first dose, 59.0% of C. natans recruits lost all tissue (died) within two to eight days of developing lesions, whereas D. labyrinthiformis recruits experienced significantly slower rates of tissue loss and minimal eventual mortality. In C. natans, larger recruits and those fused into groups of multiple genets (chimeras) exhibited the highest survivorship. In contrast, smaller and/or single (ungrouped) recruits had the lowest survivorship (9.9 - 26.5%). After 20 days, a second SCTLD dose was delivered to further test resistance in remaining recruits, and all recruits of both species succumbed within 6 days. Although no recruits showed absolute resistance to SCTLD following repeated exposures, our results provide evidence that interactions between species, size, and chimerism can impact relative resistance. This study represents the first report of SCTLD in Caribbean coral recruits and carries implications for natural species recovery and reef restoration efforts. Additional research on the susceptibility of coral juveniles to SCTLD is urgently needed, to include different species, locations, parents, and algal symbionts, with the goal of assessing relative susceptibility and identifying potential sources of resilience for this critical life history stage.

A Resident Fish Guild as a Higher Trophic Level Indicator of Oyster Reef Restoration Success

Eastern oysters (Crassostrea virginica) are critical foundation species in estuarine waters, but due to a combination of natural and anthropogenic pressures, oyster abundance has declined. Restoring oyster reefs and monitoring restoration success often focuses on oyster metrics, but relatively infrequently, responses of higher trophic level species and the production of related ecosystem services are accounted for. To address this, we compare the response of a resident reef fish guild (gobies, blennies, toadfish) to standard metrics of oyster restoration success. Using lift nets and seines, natural and restored reefs were monitored over a two-year period within Mosquito Lagoon, Florida, USA. Standard metrics are indicative of restoration success; live oyster density and reef thickness increased in restored reefs after 12 and 24 months. Combined, live oyster density and reef thickness were the best predictors of annual resident reef fish abundance compared to water quality metrics. These results suggest that the benefits of restoring oyster reef habitat are conferred to broader components of the food web, with benefits accruing to reef resident fishes that are a key trophic linkage between lower trophic level foundation species and higher trophic level predators inhabiting coastal ecosystems.

Potential coral implementation area for Indonesia Coral Reef Garden in Nusa Dua, Bali

The Indonesia Coral Reef Garden (ICRG) program is announced as a coral reef restoration program which can support the marine tourism sector since the Covid-19 pandemic hit Indonesia, particularly in Bali. A comprehensive survey and preliminary study are necessary to be conducted to decide a suitable point or to avoid a premature choice for the restoration location. Field survey in Nusa Dua, Bali was carried out on November-December 2020 to determine physical and chemical characteristics of seawater which appropriate for coral life. The bathymetry result at Nusa Dua, Bali varied from shallow to middle water depth. Area covered with coral, soft coral, coral and sand, sand, and seaweed on the seabed are found over study area. In the depth close to the seabed, the sea condition of temperature, salinity, pH, turbidity, and DO is 26.04 - 28.48 °C, 33.95 - 34.29 PSU, 7.933 - 7.982, 0.81 - 2.44 FTU, and 4.40 - 4.93 mg/L, respectively. Based on the conformity of water quality, the middle depth region has sufficient condition for coral growth. Simple Addition Weighting method is used for determining potential location. The potential coral implementation is located 3-5 km from Tanjung Benoa and in south of Nusa Dua around 1-3 km from coast.

Coral Research and Nursery Farm Project

In the framework of the Coral Management Plan for the North Field Expansion Project (NFE) and North Field Production Sustainability Project (NFPS), Qatargas has partnered with the Environmental Science Center (ESC) to develop the first land-based coral nursery in Qatar. This nursery plan includes the extraction of 1000 corals’ colonies from the NFPS and NFE pipeline corridors, north of Ras Laffan, and hence their transportation to the nursery facility, rehabilitation under controlled husbandry conditions, fragmentation, out-plantation to carefully selected recipient sites and long-term monitoring (up to 48 months). The first two batches of 200 corals were extracted in March and outplanted in April 2021. Results of the first two monitoring events, after 44 and 66 days, were quite encouraging for the seven coral genera tested. Attachment success was very high, with 92% to 97% of the outplanted fragments being detected during monitoring. No bleaching, disease or mortality was recorded so far. The coral propagation methods used in this project (i.e., fragmentation, husbandry and outplanting), although widely used, have been tested with a restricted number of branching coral species and usually in in-situ nurseries. Our project is among the first to apply this type of approach (land-based nursery) to reef restoration in the Arabian Gulf.

Linking photoacclimation responses and microbiome shifts between depth-segregated sibling species of reef corals

Metazoans host complex communities of microorganisms that include dinoflagellates, fungi, bacteria, archaea, and viruses. Interactions among members of these complex assemblages allow hosts to adjust their physiology and metabolism to cope with environmental variation and occupy different habitats. Here, using reciprocal transplantation across depths, we studied adaptive divergence in the Caribbean corals Orbicella annularis and O. franksi. When transplanted from deep to shallow, O. franksi experienced fast photoacclimation, low mortality, and maintained a consistent bacterial community. In contrast, O. annularis experienced higher mortality, and limited photoacclimation when transplanted from shallow to deep. The photophysiological collapse of O. annularis in the deep environment was associated with an increased microbiome variability and reduction of some bacterial taxa. Differences in the symbiotic algal community were more pronounced between coral species than between depths. Our study suggests that these sibling species are adapted to distinctive light environments partially driven by the algae photoacclimation capacity and the microbiome robustness, highlighting the importance of niche specialization in symbiotic corals for the maintenance of species diversity. Our findings have implications for the management of these threatened Caribbean corals and the effectiveness of coral reef restoration efforts.

Modeling Oyster Reef Restoration: Larval Supply and Reef Geometry Jointly Determine Population Resilience and Performance

Restoration of native oyster (Crassostrea virginica) populations in Chesapeake Bay shows great promise after three decades of failed attempts. Population models used to inform oyster restoration had integrated reef habitat quality, demonstrating that reef height determines oyster population persistence and resilience. Larval recruitment drives population dynamics of marine species, yet its impact with reef height and sediment deposition upon reef restoration is unknown. To assess the influence of reef height, sediment deposition and larval supply, we adapted a single-stage population model to incorporate stage structure using a system of four differential equations modeling change in juvenile density (J), and changes in volume of adults (A), oyster shell reef (R), and sediment (S) on an oyster reef. The JARS model was parameterized with empirical data from field experiments. Larval supply included larvae from the natal population and from outside populations. The stage-structured model possessed multiple non-negative equilibria (i.e., alternative stable states). Different initial conditions (e.g., oyster shell reef height) resulted in different final states. The main novel findings were that the critical reef height for population persistence and resilience was jointly dependent on sediment input and larval supply. A critical minimum larval supply was necessary for a reef to persist, even when initial sediment deposition was zero. As larval supply increased, the initial reef height needed for reef persistence was lowered, and oyster reef resilience was enhanced. A restoration oyster reef with higher larval influx could recover from more severe disturbances than a reef with lower larval influx. To prevent local extinction and assure a positive population state, higher levels of larval supply were required at greater sediment concentrations to overcome the negative effects of sediment accumulation on the reef. In addition, reef persistence was negatively related to sediment deposited on a reef prior to larval settlement and recruitment, implying that restoration reefs should be constructed immediately before settlement and recruitment to minimize sediment accumulation on a reef before settlement. These findings are valuable in oyster reef restoration because they can guide reef construction relative to larval supply and sediment deposition on a reef to yield effective and cost-efficient restoration strategies.