Coral Reefs

Feces consumption by nominally herbivorous fishes in the Caribbean: an underappreciated source of nutrients?

Abstract

Parrotfishes and surgeonfishes are major Caribbean herbivores that primarily graze reef algae and thereby play an important functional role in indirectly promoting coral recruitment and growth. Yet, an emerging body of research suggests that these nominal herbivores graze on a diverse array of other food sources and researchers have questioned whether they may target more nutrient-dense foods growing within or upon algae, such as cyanobacteria. In this study, we investigated the speciesspecific foraging rates of parrotfishes and surgeonfishes on Brown Chromis (Chromis multilineata) fecal pellets compared to other major dietary items. We found that almost 85% of observed fecal pellets were ingested by fishes and that over 90% of ingested fecal pellets were consumed by parrotfishes and surgeonfishes alone. While there were species-specific differences in the levels of feces consumption (coprophagy), we found that all three surgeonfishes (Acanthurus chirurgus, A. coeruleus, and A. tractus) and six of the nine of parrotfish species surveyed (Scarus coeruleus, S. iseri, S. taeniopterus, S. vetula, Sparisoma aurofrenatum, and S. viride) consumed C. multilineata feces. To better understand the nutritional value of this behavior, we analyzed the composition of proteins, lipids, carbohydrates, total calories, and micronutrients in C. multilineata fecal pellets and compared these to published values for other food sources targeted by these fishes. Our findings suggest that these fecal pellets may have higher values of proteins, carbohydrates, total calories, and important micronutrients, such as phosphorus, compared to various macroalgae and the epilithic algae matrix, though comparable or lower values compared to cyanobacteria. To our knowledge, this is the first study to document coprophagy by tropical herbivorous fishes in the Caribbean region. This research advances our understanding of the foraging ecology of nominally herbivorous fishes and highlights the importance of fish feces as a nutritional resource on coral reefs.

Date
2022
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Bonaire

Same but different? Zoantharian assemblages (Anthozoa: Hexacorallia) in Bonaire and Curaçao, southern Caribbean

Abstract

Marine community datasets are key to the effective management and conservation of marine ecosystems, including coral reefs, which are increasingly threatened by a myriad of stressors. Although community information exists for many comparatively well-studied taxa, other common groups remain to be examined for even such basic information. In this study, we report on the zoantharian communities (Cnidaria: Anthozoa: Hexacorallia: Zoantharia) on the reefs of Bonaire in the southern Caribbean, and compare current results from 30, 20, 10, and 5 m depths to recent similar surveys from nearby Curaçao. The surveys revealed a total of 17 zoantharian species and epibiotic associations on the reefs of Bonaire. Additionally, results showed that while zoantharian assemblages around Bonaire at shallow 5 and 10 m depths, dominated by Palythoa spp., were similar to those found on Curaçao, diversity and numbers of zoantharians were higher at 20 and 30 m due to more abundant epibiotic Parazoanthidae species associated with sponges. Differences in assemblage structure were seen in deeper 20 and 30 m depths between the two islands, implying that conservation of deeper reef slopes, or along depth gradients, may need to be independently considered and addressed for each location. Analyses with environmental parameters on the Bonaire dataset indicate the potential importance of coral reef rugosity and physical structure in shaping these zoantharian communities, aspects that should be focused on in more detail in future research.

 

Read the full article here: https://link.springer.com/article/10.1007/s00338-022-02226-x

Date
2022
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Bonaire
Curacao

Close encounters of the worst kind: reforms needed to curb coral reef damage by recreational divers

Abstract

Intentional and unintentional physical contact between scuba divers and the seabed is made by most divers and multiple times per dive, which often results in damage to corals and other marine life. Current efforts to reduce reef contacts (e.g., voluntary dive operator recognition programs and voluntary dive standards) can be effective, but lack sufficient incentive structures for longterm compliance. In their current capacity, these programs fail to reduce reef contacts to tolerable levels. Regulatory policies can facilitate pervasive and permanent shifts in human behavior, but have been underutilized to change unsustainable underwater norms. Most coral reefs open to recreational diving lie within territorial waters of individual countries, and many already have existing forms of protection with legislation that can be easily modified. Successful policy precedents in Marine Protected Areas (e.g., bans on underwater glove use) and elsewhere (e.g., antismoking laws in public spaces and legislation enforcing seat belt use) demonstrate the largely untapped potential of using effective governance to change destructive diving norms for good. To reduce intentional reef contacts, policy-makers can enact regulations in MPAs directly banning all contact between divers and the seabed. To reduce unintentional contacts, policy-makers can create policy safeguards that preempt such occurrences (e.g., requiring divers to keep a certain distance from the seabed). Crucially, such policies will need accompanying formal and informal enforcement measures that are equitable, effective, and efficient to motivate compliance and effect lasting behavior change. Having a robust, well-enforced, regulatory framework to tackle both types of reef contacts lends credence to the efforts of existing conservation programs, and is key to permanently changing divers’ underwater attitudes and fostering sustainable scuba diving behavior to the benefit of all.

Date
2021
Data type
Scientific article
Theme
Education and outreach
Research and monitoring
Journal
Geographic location
Aruba
Bonaire
Curacao
Saba
Saba bank
St. Eustatius
St. Maarten
Author

Implications of 2D versus 3D surveys to measure the abundance and composition of benthic coral reef communities

Abstract

A paramount challenge in coral reef ecology is to estimate the abundance and composition of the communities residing in such complex ecosystems. Traditional 2D projected surface cover estimates neglect the 3D structure of reefs and reef organisms, overlook communities residing in cryptic reef habitats (e.g., overhangs, cavities), and thus may fail to represent biomass estimates needed to assess trophic ecology and reef function. Here, we surveyed the 3D surface cover, biovolume, and biomass (i.e., ash-free dry weight) of all major benthic taxa on 12 coral reef stations on the island of Curaçao (Southern Caribbean) using structure-from-motion photogrammetry, coral point counts, in situ measurements, and elemental analysis. We then compared our 3D benthic community estimates to corresponding estimates of traditional 2D projected surface cover to explore the differences in benthic community composition using different metrics. Overall, 2D cover was dominated (52 ± 2%, mean ± SE) by non-calcifying phototrophs (macroalgae, turf algae, benthic cyanobacterial mats), but their contribution to total reef biomass was minor (3.2 ± 0.6%). In contrast, coral cover (32 ± 2%) more closely resembled coral biomass (27 ± 6%). The relative contribution of erect organisms, such as gorgonians and massive sponges, to 2D cover was twofold and 11-fold lower, respectively, than their contribution to reef biomass. Cryptic surface area (3.3 ± 0.2 m2 m−2planar reef) comprised half of the total reef substrate, rendering two thirds of coralline algae and almost all encrusting sponges (99.8%) undetected in traditional assessments. Yet, encrusting sponges dominated reef biomass (35 ± 18%). Based on our quantification of exposed and cryptic reef communities using different metrics, we suggest adjustments to current monitoring approaches and highlight ramifications for evaluating the ecological contributions of different taxa to overall reef function. To this end, our metric conversions can complement other benthic assessments to generate non-invasive estimates of the biovolume, biomass, and elemental composition (i.e., standing stocks of organic carbon and nitrogen) of Caribbean coral reef communities.

Date
2021
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Curacao

Impacts of parrotfish predation on a major reef-building coral: quantifying healing rates and thresholds of coral recovery

 Parrotfishes are important Caribbean herbivores that are believed to indirectly benefit corals by grazing algae; yet, some species also feed on live coral, which may have direct negative impacts on coral growth and survivorship. Caribbean parrotfishes prey upon multiple coral species but have particularly high rates of predation on Orbicella annularis , a major framework building coral and an endangered species. While some researchers have suggested that parrotfishes may have significant long-term impacts on heavily targeted species such as O. annularis , the patterns of coral recovery from parrotfish predation scars remain poorly understood. To address this knowledge gap, we tracked the fate of parrotfish bite scars on O. annularis  colonies across two Caribbean islands for up to 2 months. We evaluated differences in coral healing between islands in response to a number of variables including the initial scar surface area, scar abundance per coral colony, colony surface area, and water depth. We used these data to develop a predictive model of O. annularis  tissue loss from recent parrotfish bite scars. We then applied this model to surveys of the distribution of bite scars at a point in time to estimate long-term tissue loss of O. annularis  colonies from a standing stock of bite scars. Our findings suggest that the initial scar surface area is one of the most important predictors of coral tissue loss. The data also indicate that there are thresholds in patterns of coral tissue regeneration:we observed that small scars (B  1.25 cm2 ) often fully heal, while larger scars (C  8.2 cm2 ) had minimal tissue regeneration. The vast majority of observed scars (*  87%) were 1.25 cm2  or less, and our model predicted that O. annularis  colonies would regenerate nearly all the corresponding scar area. In contrast, while scars greater than or equal to 8.2 cm2  were infrequent (*  6% of all observed scars), our model predicted that these larger scars would account for over 96% of the total tissue loss for grazed colonies. Overall, our results suggest that the immediate negative impacts of parrotfish predation on coral tissue loss appear to be driven primarily by a few exceptionally large bite scars. While further work is needed to understand the long-term impacts of corallivory and quantify the net impacts of parrotfish herbivory and corallivory on Caribbean coral reefs, this study is an important step in addressing factors that impact the recovery of a heavily targeted and ecologically  important Caribbean coral from parrotfish predation.

Date
2020
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Bonaire

Morpho-molecular traits of Indo-Pacific and Caribbean Halofolliculina ciliate infections

Coral diseases are emerging as a major threat to coral reefs worldwide, and although many of them have been described, knowledge on their epizootiology is still limited. This is the case of the Halofolliculina ciliate infections, recognized as the skeletal eroding band (SEB) and Caribbean ciliate infection (CCI), two diseases caused by ciliates belonging to the genus Halofolliculina (Class Heterotrichea). Despite their similar macroscopic appearance, the two diseases are considered different and their pathogens have been hypothesized to belong to different Halofolliculina species. In this work, we analysed the morphology and genetic diversity of Halofolliculina ciliates collected in the Caribbean Sea, Red Sea and IndoPacific Ocean. Our analyses showed a strong macroscopic similarity of the lesions and similar settlement patterns of the halofolliculinids from the collection localities. In particular, the unique erosion patterns typical of the SEB were observed also in the Caribbean corals. Fine-scale morphological and morphometric examinations revealed a common phenotype in all analysed ciliates, unequivocally identified as Halofolliculina corallasia. Phylogenetic analyses based on nuclear and mitochondrial (COI) molecular markers consistently found all samples as monophyletic. However, although the nuclear marker displayed an extremely low intra-specific diversity, consistent with the morphological recognition of a single species, the analyses based on COI showed a certain level of divergence between samples from different localities. Genetic distances between localities fall within the intra-specific range found in other heterotrich ciliates, but they may also suggest the presence of a H. corallasia species complex. In conclusion, the presented morpho-molecular characterization of Halofolliculina reveals strong similarities between the pathogens causing SEB and CCI and call for further detailed studies about the distinction of these two coral diseases.

Date
2020
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Bonaire
Curacao
Private Document

Black spot syndrome in reef fishes: using archival imagery and field surveys to characterize spatial and temporal distribution in the Caribbean

Recently, observations of black spot syndrome (BSS) in Caribbean fishes have been linked to infection by a digenean trematode parasite, Scaphanocephalus expansus. Recently, This study examined the distribution of BSS over multiple spatial and temporal scales: at the island scale in Bonaire, Dutch Caribbean, using field surveys of 4885 fish belonging to three species, and across the wider Caribbean through analysis of 2112 images from Google Images searches (1985–2013). The field surveys in Bonaire indicated that the prevalence (% of individuals affected with BSS) and intensity (severity of BSS measured in 3 stages) were highest in Acanthurus tractus (prevalence 61.8%, including 30.1% in stage 3) followed by Sparisoma aurofrenatum (prevalence 48.3%, 24.1% in stage 3) and lowest in Caranx ruber (prevalence 38.5%, 3.3% in stage 3). Prevalence and intensity of BSS decreased significantly with survey depth (e.g., 2 m: prevalence 68.0%, 22.0% in stage 3; 18 m: prevalence 36.2%, 4.0% in stage 3) and were significantly lower in 2012 than in 2017 (prevalence: 59.3% in 2012, 68.7% in 2017; stage 3: 16.3% in 2012, 25.1% in 2017). The Southeast of Bonaire had significantly lower prevalence of BSS (16.4%) than the other four regions and lower intensity (11.7% in stage 3) than all regions but the Southwest. The Google Images searches querying for ocean surgeonfish, A. tractus and A. bahianus, identified pictures from 26 wider Caribbean locations; BSS was detected in 14 locations of which 13 were new, with the first detection dating back to 1985 in Bonaire. The Southern Caribbean had significantly higher prevalence of BSS (78.1%) than other ecoregions (0–34.6%), and Bonaire was identified as a hotspot, highlighting the utility of mining websites for archival imagery to quantify spatial and temporal patterns in disease phenomena. This study demonstrates how visible signs of parasite infection can be used to find differences in parasite prevalence and loads on a reef, island and sea scale.

Date
2019
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Bonaire
Author

Nitrogen fixation and diversity of benthic cyanobacterial mats on coral reefs in Curaçao

Benthic cyanobacterial mats (BCMs) have increased in abundance on coral reefs worldwide. However, their species diversity and role in nitrogen fixation are poorly understood. We assessed the cyanobacterial diversity of BCMs at four coral reef sites in Curaçao, Southern Caribbean. In addition, nitrogen fixation rates of six common mats were measured. Microscopic examinations showed 22 cyanobacterial species, all from the order Oscillatoriales. Species diversity was similar among sites despite differences in overall BCM abundance. Dominant mats were primarily composed of Hydrocoleum glutinosum, Oscillatoria bonnemaisonii or Lyngbya majuscula. However, some mats exhibited highly variable species composition despite consistent macroscopic appearance. 16S rRNA-based phylogeny revealed similar species as those identified by microscopy, with additional sequences of unicellular (Xenococcus and Chroococcidiopsis) and heterocystous (Rivularia and Calothrix) cyanobacteria. Vice versa, morphotypes of Tychonema, Schizothrix and Dichothrix were found by microscopy only. The detection of similar species at the same sites in a study conducted 40 years ago indicates that changes in environmental conditions over these years may have favored indigenous species to bloom, rather than facilitated the introduction and proliferation of invasive species. Nitrogen fixation rates of mats were 3–10 times higher in the light than in the dark. The highest areal nitrogen fixation rate (169.1 mg N m−2 d−1) was recorded in the cyanobacterial patch dominated by O. bonnemaisonii. A scale-up of nitrogen fixation at a site with 26% BCM cover at 7 m depth yielded an aerial rate of 13 mg N m−2 reef d−1, which exceeds rates reported in open ocean blooms of Trichodesmium in the Caribbean. Our results suggest that the Caribbean basin is not only a hotspot for planktonic nitrogen fixation, but also for benthic nitrogen fixation. Because BCMs fix vast amounts of nitrogen, their proliferation will strongly alter the nitrogen budget of coral reefs.

Date
2018
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Curacao

Antagonistic behavior between two honeycomb cowfish, Acanthostracion polygonius Poey, 1876, at Curaçao

The honeycomb cowfish, Acanthostracion polygonius Poey, 1876 (Ostraciidae) is easily distinguishable from other Caribbean coral reef fish. Both females and males possess a heavy external bony box with uniformly hexagonal scale plates as armor, as well as a pair of spines projecting from the carapace above the eyes and anterior to the £ fin (Moyer 1984). They are known to feed on a variety of invertebrates, including tunicates, alcyonaceans, shrimps, gastropods, and at least 15 species of sponges (Randall 1967; Wulff 1994).

During a coral reef biodiversity survey at Curaçao (June 2017), two A. polygonius individuals were engaged in what appeared to be either a failed mating ritual dance or a male–male territorial dispute (Fig. 1). It is likely that the encounter is that of a male–male confrontation since the distinctive humming sound of the male prior to gamete release was not heard, nor any spawning was observed (Moyer 1984).

The fighting behavior resembled that of Lactoria diaphana from the Indo-Pacific; upon seeing each other, the pair proceeded to flash and display their bright neon-blue coloration (Moyer 1984). Aggressively charging each other, they took turns sucking/biting their respective underside belly as they rose in the water column (from 6 m depth) in a circular motion (Fig. 1). Upon reaching the proximity of the surface, with the larger (more dominant) trunkfish attached to the smaller fish, the pair broke off and swam toward the reef in opposite directions. Within the scientific literature, little is known regarding cowfish social structure, reproduction, and territorial competition. This record shines light into a previously known ritual, yet still misunderstood behavior of trunkfishes in the Caribbean.

Date
2018
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Curacao

Damage to the leeward reefs of Curac¸ao and Bonaire, Netherlands Antilles from a rare storm event: Hurricane Lenny, November 1999

Fringing reefs along the southwestern shores of the Caribbean islands of Curaçao and Bonaire (12°N), located outside the most frequent hurricane tracks, are rarely affected by heavy wave-action and major storms, yet have experienced disturbances such as coral bleaching, coral diseases, and mass mortalities. The last major hurricane to hit these islands occurred over 100 yr ago. In November 1999, Hurricane Lenny took an unusual west-to-east track, bisecting the Caribbean Basin and passing approximately 200 miles north of Curaçao and Bonaire. The leeward shores of both islands were pounded for 24 h by heavy waves (~3–6 m) generated while the storm was centered far to the west. Reef damage surveys at 33 sites conducted between November 1999 to April 2000, following the storm, documented occurrences of toppling, fragmentation, tissue damage, bleaching, and smothering due to the storm. Reefs were severely damaged along westward-facing shores but less impacted where the reef front was tangential to the wave direction or was protected by offshore islands. At the most severely damaged sites, massive coral colonies 2–3-m high (older than 100 yr) were toppled or overturned, smaller corals were broken loose and tumbled across the shallow reef platform and either deposited on the shore or dropped onto the deeper forereef slope. Branching and plating growth forms suffered more damage than massive species and large colonies experienced greater damage than small colonies. Toppled massive corals have a high potential of preserving the event signature even if they survive and continue to grow. Reorientation of large, long-lived coralla may provide a unique indicator of disturbance in a reef system rarely affected by hurricanes. At some locations, wave scouring removed loose sediment to reveal a cemented framework of Acropora cervicornis rubble on the shallow platform above 10-m depth. This rubble was generated in situ, not by storm processes, but rather by an earlier mass mortality of thickets of staghorn coral that covered extensive areas of the shallow platform prior to the incidence of white band disease in the early 1980s.

Date
2004
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Bonaire
Curacao