Assisted gene flow (AGF) is a conservation intervention to accelerate
species adaptation to climate change by importing genetic
diversity into at-risk populations. Corals exemplify both the need for
AGF and its technical challenges; corals have declined in abundance,
suffered pervasive reproductive failures, and struggled to adapt to
climate change, yet mature corals cannot be easily moved for breeding,
and coral gametes lose viability within hours. Here, we report
the successful demonstration of AGF in corals using cryopreserved
sperm that was frozen for 2 to 10 y. We fertilized Acropora palmata
eggs from the western Caribbean (Curaçao) with cryopreserved
sperm from genetically distinct populations in the eastern and central
Caribbean (Florida and Puerto Rico, respectively). We then confirmed
interpopulation parentage in the Curaçao–Florida offspring
using 19,696 single-nucleotide polymorphism markers. Thus, we
provide evidence of reproductive compatibility of a Caribbean coral
across a recognized barrier to gene flow. The 6-mo survival of AGF
offspring was 42%, the highest ever achieved in this species, yielding
the largest wildlife population ever raised from cryopreserved
material. By breeding a critically endangered coral across its range
withoutmoving adults, we show that AGF using cryopreservation is
a viable conservation tool to increase genetic diversity in threatened
marine populations.

There has been a recent increase in public awareness of environmental issues as the effects of climate change have become ever more noticeable in our daily lives. As we enter a new decade, it becomes useful to review what conservation efforts have worked so far, and take inventory of what efforts will be required for the future. Starting with the constitutional referendum creating the Caribbean Netherlands (Bonaire, St. Eustatius and Saba (BES), the response to conservation challenges of all six Dutch Caribbean islands have varied. Since 2010, the BES islands have seen an overall increase in funding support and conservation actions, and therefore presumably also saw greater improvements when compared to Aruba, Curaçao and Sint Maarten, though clearly not enough (Sanders et al, 2019).

The goal of this Transboundary Species special edition of BioNews is to provide an update on the latest published research results and highlight the need for transboundary protection. These species know no boundaries, and thus move between the Dutch Caribbean islands and beyond. Their protection will require broadscale conservation efforts which cover the entire Caribbean, including the six Dutch Caribbean islands. Collaboration between all six islands is of the utmost importance. This is one of the Dutch Caribbean Nature Alliance’s (DCNA) main goals: working together and sharing skills, knowledge and resources to maintain a solid network and support nature conservation in the entire Dutch Caribbean.

• zone    DO = DROP-OFF at ~10m depth, LT= Lower Terrace at ~5m depth
• length transect in cm
• rugosity    measure for 3-dimensional complexity reef:  length transect following substrate (cm) / plain length transect (cm)
• Average heigh in cm of coral colonies along transect
• date
• Depth in meters
• start.time   
• end.time  
• latitude
• longitude
• Crustose coralline algal cover (proportion)
• Coral cover (proportion)
• cayno bacterial cover (proportion)
• macroalgal cover (proportion)
• other cover (proportion)
• rubble cover (proportion)
• sand cover (proportion)
• soft coral cover (proportion)
• sponge cover (proportion)
• bare substrate cover (proportion)
• turf cover (proportion)
• Transect to left (L) from starting point and to right (R) from starting point
• MPA=Marine Protected Area, ND=No Diving, NF=No Fishing
• Entry into water, either from boat or from shore
  
   

Coral reefs fulfil many ecological functions such as maintaining the diversity, providing habitats and

shoreline protection. One of the most important reef building corals is the Aropora cervicornis known

as Staghorn. Over the past decades many corals have disappeared due to human and natural disturbances.

Acropora species populations are also heavily damaged in the Caribbean since the 1980s by the

white band disease (WBD). Also predation and competition between organisms can influence the

growth and survival of corals. The Acropora species A. cervicornis is an important reef building coral

which can be a dominant species because of their relative fast growing abilities. This gives them the

ability to overgrow other soft and stony corals. However algal growth is faster than the growth of A.

cervicornis, making the coral species susceptible to be overgrown by other organisms besides corals.

Reefs can get overgrown by algae like seen around Saba, a small island in the Dutch Caribbean. Together

with St. Maarten, St. Eustatius and the Turks and Caicos Islands Saba is part of the RESCQ (Restauration

of Ecosystem Services and Coral reef Quality) project. This project aims to restore Acropora

populations included the A.cervicornis by establishing a coral nursery. In this research the influence of

predation and competition of other species on the growth and fitness of A.cervicornis will be studied.

In this experiment A.cervicornis fragments were planted on the reef where different cleaning treatments

were tested. Depending on the treatment the area around the planted fragments was cleaned

from algae. Eventually 14 out of 15 fragments were healthy with a positive growth rate, there was no

significant difference between the cleaning treatments. Some fragments showed predation signs such

as spot-biting, but after polyp-recovery the fragments gained a positive growth.

Previously dominant, reef-building Acropora cervicornis and A. palmata abundance decreased dramatically in the Caribbean in the 1970s, mainly due to the white band disease. They have been on the IUCN Red List as ‘critically endangered’ species since 2008, but restoration efforts already date back to the year 2000. Of these methods, fragmentation used in coral gardening seems to be the most productive method for these species, but there is a need for optimisation of this process. This research filled up the nurseries of Saba, Dutch Caribbean, with Acropora, measured growth of both species and of the two staghorn mother colonies. Furthermore, some staghorn fragments were outplanted on an outplanting structure. Growth rates of staghorn differed between some trees, with the highest growth rates in the cut fragments that were ready for outplanting and therefore have lived in the nursery for the longest time. The outplants themselves showed a lower growth rate, which might have to do with the structure itself. There was generally no correlation between initial primary branch length and growth rates of staghorn found except for one tree. Furthermore, branching corals grew faster than non-branching corals, independent of the amount of side branches. Side branches tend to appear from about 10 cm length, but half of the fragments without side branches did not branch at all in the maximum of 79 days. Side branching over time seems to follow an exponential model, but prolonged measurements are needed to prove this. Elkhorn growth in surface area and perimeter was found already in a short period of time, but the method used must be further improved. The results of this research can be used to improve coral gardening of Acropora spp.

MSc thesis.

With the SCUBA diving industry growing at a reate of 7% per annum and a major qualifying agency havig just certified its 10 millionth diver, an increasing amount of direct pressure is being placed on marine organisms. In many tropical areas, diving tourism is concentrated in a small area and is often seen to be having an impact on bethic organisms....This study looks in detail at the role of SCUBA activity in coral divesrity maintenenace, and assesses its significace as a disturbance to the reefs of Bonaire

Elkhorn (Acropora palmata) and staghorn (A. cervicornis) corals were listed as threatened under the ESA on May 9, 2006. Elkhorn and staghorn corals were once the most abundant and important species on Atlantic/Caribbean coral reefs in terms of building reef structure. Both elkhorn and staghorn corals underwent precipitous declines in abundance throughout their ranges. No single or collective group of threats may impact all regions of these species’ ranges equally. Multiple threats acting synergistically or cumulatively likely compound impediments to recovery among elkhorn and staghorn coral populations. The threats to these species that are impeding recovery are: disease, increasing
temperature, depensatory population effects, loss of recruitment habitat, sedimentation, anthropogenic abrasion and breakage, predation, inadequacy of existing regulatory mechanisms, natural abrasion and breakage, ocean acidification, and nutrients and contaminants.

The purpose of this recovery plan is to identify a strategy for rebuilding and assuring the long-term viability of elkhorn coral and staghorn coral populations in the wild, allowing ultimately for the species’ removal from the federal list of endangered and threatened species. Actions must be taken to address ocean warming and acidification impacts on these species. Simultaneously, local threat reductions, mitigation strategies, and in and ex situ conservation and restoration actions must be pursued.

The goal of this recovery plan is to increase the abundance and to protect the genetic diversity of elkhorn and staghorn coral populations throughout their geographical ranges while sufficiently abating threats to warrant delisting of both species.

The NOAA Coral Reef Watch program uses satellite data to provide current reef environmental conditions to quickly identify areas at risk for coral bleaching. Bleaching is the process by which corals lose the symbiotic algae that give them their distinctive colors. If a coral is severely bleached, disease and death become likely.

Coral Reef Watch also offers a modeled Outlook that predicts the likelihood of coral bleaching heat stress on a week-by-week basis, up to four months in the future (the typical length of a bleaching season).

Continuous satellite monitoring of sea surface temperature at global scales and modeled predictions of approaching bleaching-level heat stress provide resource managers, scientific researchers, and other coral reef ecosystem stakeholders with tools to understand and better manage the complex interactions leading to coral bleaching. When bleaching conditions occur, these tools can be used to trigger bleaching response plans and support appropriate management decisions and communication with the public.

The conservation status of 845 zooxanthellate reef-building coral species was assessed by using International Union for Conservation of Nature Red List Criteria. Of the 704 species that could be assigned conservation status, 32.8% are in categories with elevated risk of extinction. Declines in abundance are associated with bleaching and diseases driven by elevated sea surface temperatures, with extinction risk further exacerbated by local-scale anthropogenic disturbances. The proportion of corals threatened with extinction has increased dramatically in recent decades and exceeds that of most terrestrial groups. The Caribbean has the largest proportion of corals in high extinction risk categories, whereas the Coral Triangle (western Pacific) has the highest proportion of species in all categories of elevated extinction risk. Our results emphasize the widespread plight of coral reefs and the urgent need to enact conservation measures. 

The evolution of tolerance to future climate change depends on the standing stock of genetic variation for resistance to climate-related impacts [1, 2], but genes contributing to climate tolerance in wild populations are poorly described in number and effect. Physiology and gene expression pat- terns have shown that corals living in naturally high-temper- ature microclimates are more resistant to bleaching because of both acclimation and fixed effects, including adaptation [3]. To search for potential genetic correlates of these fixed effects, we genotyped 15,399 single nucleotide polymor- phisms (SNPs) in 23 individual tabletop corals, Acropora hyacinthus, within a natural temperature mosaic in backreef lagoons on Ofu Island, American Samoa. Despite overall lack of population substructure, we identified 114 highly divergent SNPs as candidates for environmental selection, via multiple stringent outlier tests, and correlations with temperature. Corals from the warmest reef location had higher minor allele frequencies across these candidate SNPs, a pattern not seen for noncandidate loci. Furthermore, within backreef pools, colonies in the warmest microcli- mates had a higher number and frequency of alternative alleles at candidate loci. These data suggest mild selection for alternate alleles at many loci in these corals during high heat episodes and possible maintenance of extensive polymorphism through multilocus balancing selection in a heterogeneous environment. In this case, a natural popu- lation harbors a reservoir of alleles preadapted to high temperatures, suggesting potential for future evolutionary response to climate change.