Coral reefs

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.

Koraalriffen zijn de belangrijkste economische hulpbron voor de eilanden van Caribisch Nederland. Zij verkeren in een slechte toestand en zonder actief ingrijpen zullen zij binnen afzienbare tijd verdwijnen. Het is meer dan ooit duidelijk dat de gevolgen van klimaatverandering onafwendbaar op ons afkomen. Dit zal leiden tot meer stress voor de omgeving waarin mensen leven en waarvan ze afhankelijk zijn. Voor de toekomst van Bonaire, Saba en St. Eustatius is het noodzakelijk om een gemeenschappelijke milieu- en natuurvisie te ontwikkelen, daadkrachtig besluiten te nemen en op korte termijn te beginnen met de uitvoering zodat de veerkracht van de natuur van Caribisch Nederland weer omhoog gaat en beter bestand zal zijn tegen de gevolgen van klimaatverandering. De komende 10 jaar zijn cruciaal wil men het tij nog keren. Door nieuw beleid kan de economie omgebogen worden in de richting van een duurzame toekomst waarbij banen behouden worden en negatieve effecten van globale en regionale veranderingen zoveel mogelijk kunnen worden opgevangen door veerkrachtige ecosystemen te realiseren. Dit kan door lokale stressfactoren zoveel mogelijk te minimaliseren. In dit rapport proberen we handvatten aan te reiken voor de ontwikkeling van deze visie en geven we mogelijke oplossingsrichtingen aan gebaseerd op de huidige stand van de wetenschap ten aanzien van duurzaam beheer van koraalrifecosystemen.

Contents

Introduction - by the Editors.
Address - by M. A. POURIER, Minister of Economic Development.
Address- by Mr. A. R. W. SINT JAGO, Lieutenant Governor of Bonaire.
Illuminated Address to Mr. L. D. GERHARTS- by Mr. J. A. CONNELL, President Caribbean Conservation Association.

I.            FLAMINGOES

J. Rooth: Ecological aspects of the flamingos on Bonaire. Resumen: Aspectos ecológicos de los flamencos en Bonaire.
A. Sprunt: A new Colombian site for the American flamingo (Phoenicopterus ruber).
B. de Boer & J. Rooth: Notes on a visit to Chichiriviche (Venezuela).
I. Kristensen: Discussion on flamingo problems.
 

II.           0IL POLLUTION

J. H. B. W. Elgershuizen & H. A. M. de Kruijf: abstract: Toxic effects of crude oils and dispersant to the stony coral Madracis mirabilis,
J. H. B. W. Elgershuizen, R. P. M. Bak & I. Kristensen: abstract: Oil sediment removal in corals.
H. S. George: Position-determination of oil pollution by aerial photographs and its interpretation.
L. T. Giulini: La contaminación del ambiente marino por los hidrocarburos. Abstract: Marine pollution by oil.
G. P. Canevari: Some remarks regarding the utility and mechanisms of chemical dispersants.
 

III.          REEFS

J. L. Hunt & J. Araud: Coral distribution in the Bahia de Patanemo, Venezuela.
H. G. Gamiochipi: Parques submarinos en el Caribe Mexicano.
C. Noome & I. Kristensen: abstract: Necessity of conservation of slow growing organisms like Black Coral. Resumen: Necesidad de medidas conservacionistas con respecto a organismos de lento crecimiento tales como el Coral Negro.
A. Corsten, I. Corsten-Hulsmans & H. A. M. de Kruijf: abstract: Recolonization experiments of the coral reef fish Gramma Ioreto, the Royal Gramma.
C. den Hartog: The role of seagrasses in shallow waters in the Caribbean.
E. Towle: abstract: Reef communities and human interference: a positive view.
D. Stewart: abstract: Human participation in reef communities.
 

Addresses of the authors.
List of participants.
Netherlands Antilles National Parks Foundation- information.
 

Invasive lionfish are assumed to significantly affect Caribbean reef fish communities. However, evidence of lionfish effects on native reef fishes is based on uncontrolled observational studies or small-scale, unrepresentative experiments, with findings ranging from no effect to large effects on prey density and richness. Moreover, whether lionfish affect populations and communities of native reef fishes at larger, management- relevant scales is unknown. The purpose of this study was to assess the effects of lionfish on coral reef prey fish communities in a natural complex reef system. We quantified lionfish and the density, richness, and composition of native prey fishes (0–10 cm total length) at sixteen reefs along ∼250 km of the Belize Barrier Reef from 2009 to 2013. Lionfish invaded our study sites during this four-year longitudinal study, thus our sampling included fish community structure before and after our sites were invaded, i.e., we employed a modified BACI design. We found no evidence that lionfish measurably affected the density, richness, or composition of prey fishes. It is possible that higher lionfish densities are necessary to detect an effect of lionfish on prey populations at this relatively large spatial scale. Alternatively, negative effects of lionfish on prey could be small, essentially undetectable, and ecologically insignificant at our study sites. Other factors that influence the dynamics of reef fish populations including reef complexity, resource availability, recruitment, predation, and fishing could swamp any effects of lionfish on prey populations. 

Protecting Marine Life Through Education, Service, and Research

REEF was founded in 1990, out of growing concern about the health of the marine environment, and the desire to provide the SCUBA diving community a way to contribute to the understanding and protection of marine populations. REEF achieves this goal primarily through its volunteer fish monitoring program, the REEF Fish Survey Project. Participants in the Project not only learn about the environment they are diving in, but they also produce valuable information. Scientists, marine park staff, and the general public use the data that are collected by REEF volunteers.

Mission

REEF conserves marine environments worldwide. Our mission is to protect biodiversity and ocean life by actively engaging and inspiring the public through citizen science, education, and partnerships with the scientific community.

Vision

REEF envisions divers and marine enthusiasts actively engaging in marine conservation. With knowledge, training and the opportunity to get involved, these marine citizen scientists make significant and ongoing contributions through REEF’s strategic partnerships with government agencies, science and academic institutions, the non-profit sector, and local communities. Divers and snorkelers are in a unique position to observe and document the many valuable and vulnerable living marine resources. They play an important role in bringing information to the surface that adds to the knowledge base of ocean ecosystems and facilitates informed decision-making. Through REEF’s efforts, marine citizen scientists impart an ethic of stewardship to current and future generations.

The ecosystems of the island of Bonaire support a range of activities that depend on the quality of the natural environment. Tourism is one of these activities and it represents an important source of income for the local economy. Tourism in Bonaire can be divided in stay-over tourism and cruise tourism. Whether further development of cruise tourism is desirable for Bonaire is constantly under discussion. It is thought that more cruise tourists will contribute to economic growth. But, at the same time, there is a fear that an increase in the number of cruise tourists and the investments in infrastructure and other facilities to facilitate this growth will put extra pressure on the ecosystems. And these are the same ecosystems that are vital in attracting not only cruise tourists, but also stay-over tourists.

This study aims at providing quantitative and qualitative information on the potential benefits and negative effects of an expansion of the cruise tourism industry on Bonaire. For this purpose, a socio-economic valuation was first conducted to understand the cruise tourism industry in Bonaire. This resulted in insights that include tourist’s expenditures, the different actors on the island that benefit from these expenditures, the dependency of certain sectors on tourism related revenues and the attitude of tourists towards certain social and environmental changes in the island. This information is derived from tourist surveys, a business survey and literature review.

Second, with the information gathered, and making use of an economic Input-Output model for Bonaire that is linked to an ecologic model, three different cruise tourism growth scenarios were analysed: a baseline scenario, a moderate growth scenario and a rapid growth scenario. This analysis resulted in the calculation of economic benefits that would result from an increase in the number of cruise tourists in each scenario. At the same time, using the ecologic module that is linked to the economic Input-Output model, the socio-environmental impact on a number of natural indicators was also assessed. Certain environmental effects of cruise tourism, like waste production, water consumption and the ecologic footprint of cruise ships, could not be included in the ecologic module and were, therefore, assessed separately from the model.

The surveys conducted amongst tourists have shown the importance of maintaining a healthy reef and the tranquillity on the island. Especially stay-over tourists indicated that they are not willing to return to a more crowded island or an island with a degraded coral reef. Both the survey and the scenario analysis indicate that sectors that benefit the most from the growth of the cruise industry are the transport, restaurant, ‘other services’ (which include tour operators) and trade sectors.

The scenario analysis further indicates that an increase in cruise tourism will generate a growth in GDP within the period of the analysis (until 2024). While the economy grows as a whole, more jobs will be generated. However, given the seasonal character of cruise tourism and the sectors that benefit the most from it, most of the jobs created appear to be in lower income categories. As a result of potential population growth to fill in these new jobs, household consumption and GDP per capita do not increase as much as the GDP growth might suggest. Household consumption at the end of the analysis period (2024) is only $234 higher in the rapid growth scenario compared to the baseline scenario.

The economic growth caused by cruise tourism expansion also results in socio-environmental impacts, as higher number of visitors will increase direct pressures on the ecosystems that are visited. The main impacts that have been analysed are change in land use, decrease in coral cover, water consumption and waste generation and the potential decrease of stay-over tourists as a result of coral reef degradation and more built-up land.

However, not all potential socio-environmental impacts could be included in the scenario analysis. If cruise tourism industry is to expand even further, Bonaire must expand its infrastructure. This means that investments need to be made to accommodate larger amounts of tourists. The scenario analysis does not take into account the impact of these potential infrastructure projects like additional port infrastructure, proper waste management system, water management, more roads and more ground transportation. It was also not possible to assess the effects on the environment and the return rate of stay-over tourists caused by crowding in specific areas and on peak moments.

The results of the study demonstrate that there are external effects related to the expansion of cruise tourism. For example, a decrease in stay-over tourists as a result of rapid growth of the cruise tourism industry may have significant implications for the hotel industry. To make decisions regarding cruise tourism expansion, such external effects should be taken into account. Furthermore, investing on an environmental friendly expansion and the enforcement of environmental regulations will also be of high importance to avoid endangering the ecosystems and, thereby, the tourism industry as a whole. More research on the local impacts of cruise tourism and the effects on the stay-over sector are necessary to draw conclusions on the desirability of the expansion of cruise tourism for the island.

To follow the health of the coral reefs of Bonaire and Curacao a number of locations on each island are photographed each year since 1973. At each location a 3 m square at up to 4 different depths is recorded and analysed.

Please contact Wageningen Marine Research for more information.

The stoplight parrotfish, Sparisoma viride, is one of the dominant herbivores on the reefs of Bonaire. The effects of macroalgae herbivory have been well documented but the potential of S. viride to act as a shuttle for zooxanthellae remains unknown. Although coral is not considered a food item of S. viride they occasionally bite living tissue off of colonies of the scleractinians Montastrea annularis and Colpophyllia natans. Coral tissues contain large amounts of symbiotic dinoflagellates of the genus Symbiodinium, commonly referred to as zooxanthellae. Symbiodinium may be the key primary producer of the reef ecosystem and are found almost exclusively in symbiotic relationships with cnidarians. It is the aim of this article to examine the potential role of S. viride as a vector for transport of Symbiodinium throughout the reef environment as a result of parrotfish white spot biting. The purpose of coral biting is not known but territoriality is suspected in focused biting. Depending on the effect of parrotfish ingestion on the Symbiodinium cells, parrotfish white spot biting behavior could result in transport of Symbiodinium throughout the reef environment, increasing the genetic diversity of zooxanthellae populations.

This student research was retrieved from Physis: Journal of Marine Science I (Fall 2006)19: 33-37 from CIEE Bonaire.

A reoccurring problem facing a majority of the coral reefs in the Caribbean for the past few decades has been the fear of a changing community structure from primarily reef-building corals to algal dominance. A shift in such ecosystems could inhibit coral growth and recruitment, eventually killing corals and lowering the diversity of fish in the area. Recent developments in agriculture and technology have advanced the dispersal of various inorganic nutrients into water systems, where excess nitrogen or phosphorous levels may lead to an increase in algal photosynthesis and thus growth. For my study I looked at relationships between algal growth and nutrient levels in seawater, specifically ammonia and nitrates + nitrites. Using photography and underwater transects I looked for differences in the amount of algae at sites with high or low nutrient levels as measured in March 2006 by the Bonaire Marine Park (BMP). The site with the highest nitrate + nitrite levels had a mean algal cover of 30.6% (std. dev. 30.4), which was not statistically different from the site with lowest concentrations (mean algal cover = 22.9%, std. dev. = 23.1). Algal cover was highest at 18 Palms (mean = 38.6% std. dev. = 39.5), where the lowest ammonia concentration was found. This research showed that nutrient levels did not influence the percent algal cover at my sites. Possible reasons for these findings are discussed.

This student research was retrieved from Physis: Journal of Marine Science I (Fall 2006)19: 21-25 from CIEE Bonaire.

The number and type of diver contacts with coral reefs on Bonaire and Klein Bonaire’s fringing reefs were studied in fall 2006. The goal of this study was to observe the number of contacts recreational SCUBA divers are making with the local reefs. Twenty four divers were chosen haphazardly and followed for 30 minute observation periods on three shore dives and seven boat dives. Forty-one percent of observed divers came in contact with the reef substrate at least once during the observation period for a total of 84 contacts. Contacts were categorized as fin taps, body bumps, skin contacts, sediment upsets and equipment dragging. The majority of observed contacts were fin taps, followed by skin contacts, sediment upsets, equipment dragging and body bumps. The following diver attribute categorizes were analyzed to determine the relationship between contact rate and diver attributes: dive access type (shore vs. boat), gender of the diver, skill level of the diver (beginner vs. advanced), and presence or absence of camera equipment. Shore dives, female divers, beginner divers and underwater photographers all demonstrated higher numbers of contacts than their counterparts with female divers contacting the reef nearly twice as often as males. A one-way ANOVA was used to analyze the number of contacts between the divers in each of the above categories. There were no statistically significant differences in number of contacts within any of the categories. The lack of statistically significant differences may be a result of the relatively small sample size, short study period, or a combination of the two.

This student research was retrieved from Physis: Journal of Marine Science I (Fall 2006)19: 7-12 from CIEE Bonaire.