Algae

40 years of change on the coral reefs of Curaçao and Bonaire

Coral reef ecosystems

Tropical coral reefs are among the most productive and biologically diverse ecosystems found on earth (Odum and Odum 1955; Connell 1978; Moberg and Rönnbäck 2003). Although these reefs only cover 0.1 – 0.5% of the ocean floor they provide a home to almost one third of the marine fish species and other marine biota (Mcallister 1991; Spalding and Grenfell 1997; Spalding et al. 2001). Like rainforests, their terrestrial equivalent, the three-dimensional habitat complexity underpins the biological success of coral reef systems (Connell 1978; Grigg et al. 1984; Reaka-Kudla 1997). This structural framework is primarily provided through the precipitation of vast quantities of calcium carbonate by scleractinian corals (Goreau 1959b; Goreau and Goreau 1959; Smith and Kinsey 1976). Basic growth of coral skeleton forms the fundament of the reef and facilitates complex ecosystem functioning and niche partitioning to harbour an exceptional heterogeneity of associated biota (Connell 1978; Graham and Nash 2012; Kennedy et al. 2013; Newman et al. 2015). Ancillary to the inexpressible biological value, millions of people worldwide rely in some way on the services provided by coral reefs, most notably for nourishment, but also for services associated with tourism and coastal protection (Costanza et al. 1997; Moberg and Folke 1999; Moberg and Rönnbäck 2003). By increasing frictional dissipation of wave energy, the complex physical structure created by corals protects coastal shorelines from erosion. This has allowed humans to settle and develop coastal areas throughout the tropics. Yet, coral reefs are at present ubiquitously under pressure due to a variety of stressors associated with increased anthropogenic activity on a global and local scale.

The marine environment is continuously exposed to change, but currently this change is more and more the result of human actions (Harvell et al. 1999; Derraik 2002; Orr et al. 2005; HoeghGuldberg and Bruno 2010). The stress exerted by the natural and anthropogenic induced changing global environment works in synergy with stressors that act on a finer spatial scale. Factors such as the overharvesting of fish, pollution, eutrophication, coastal development and the introduction of invasive species can locally trigger shifts in community composition and trophic hierarchy (Hughes 1994; Hughes et al. 2003; Pandolfi et al. 2003; Hughes et al. 2007; Hughes et al. 2017). By destabilising ecosystem functioning and interactions between key species, these stressors reduce reef resilience and therewith the capacity of coral reefs to cope with globally induced sea surface temperature anomalies or ocean acidification (Pandolfi et al. 2003; Bellwood et al. 2004; Hughes et al. 2017). Reefs in the wider Caribbean region seem particularly vulnerable to anthropogenic impact (Jackson et al. 2014). By large this can be ascribed to increased local pressures associated with the unprecedented human population expansion in the region. Since the 1950s, the total population in the Caribbean has more than doubled (United Nations, Department of Economic and Social Affairs, Population, Division, 2015). Natural biological and hydrological conditions are also less favourable compared to, for instance, the Indo-Pacific region (Roff and Mumby 2012). Biological diversity in the IndoPacific exceeds 10-fold the diversity found in the Caribbean (Spalding et al. 2001; Hoeksema et al. 2017), implying limited functional redundancy in the latter (Bellwood et al. 2003; Bellwood et al. 2004; Jackson et al. 2014). In addition, the quality of Caribbean surface water is significantly impacted by discharge from major South-American rivers like the Amazon and Orinoco as well as the North-American Mississippi river. The residence time of the polluted and eutrophic water from these rivers, combined with run-off and sewage water from the numerous islands is relatively long in the Caribbean Sea due to its distinct basin-like morphological and hydrological features (Roff and Mumby 2012). As a consequence of the rapid anthropogenic alteration of the marine environment we now see an ecological degradation of Caribbean coral reef habitats that has not occurred for over 200.000 years (Pandolfi and Jackson 2006).

Date
2019
Data type
Research report
Theme
Research and monitoring
Report number
Thesis
Geographic location
Bonaire
Curacao

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

A quantitative study of the seagrass and algal meadows of the Spaanse Water, Curaçao, the Netherlands Antilles

The Spaanse Water is a relatively turbid, 3.19 km2 inland bay of virtually oceanic salinities and contains the largest seagrass, algal and mangrove areas of the Curaçao Underwater Park. During 1989 and 1990, a quantitative community assessment of the larger attached flora and fauna of the seagrass and algal meadows of the bay was conducted at 151 6 m2 stations using a quadrat sampling technique.

A total of 13 different assemblages were distinguished. Shallow assemblages were dominated by Thalassia testudinum and Halimeda opuntia. As depth increased and light levels decreased, Thalassia gave way to increased coverages of especially H. opuntia, H. incrassata, Cladophora sp. and Caulerpa verticillata. In areas with significant availability of hard substrate an assemblage characterised (though not dominated) by corals was found at depths of 0–2 m, while sponges were concentrated at depths of about 4 m. The richest assemblages were found in shallow areas with high light levels and where a mix of both hard and soft substrate occurred. Assemblages with the lowest species richness were typically associated with low light intensities, soupy muds or homogeneous sandy sediments of high grain size.

Date
1996
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Curacao

Some Notes on Charophyta Collected in The Netherlands West Indies, North Venezuela and Colombia

In 1930 Mr. P. Wagenaar Hummelinck made an excursion to Curacao, Aruba, and Bonaire with the main object of studying the land and freshwater fauna. In 1936 and 1937 he again visited these islands and, moreover, a.o. the island of Margarita off the Venezuelan coast, the Venezuelan peninsula Paraguana and the Colombian peninsula La Goajira (Wagenaar Hummelinck, 1940). In the various inland-waters also Algae and Phanerogams have been collected. The aquatic Phanerogams were described by Van Ooststroom (1939); the Charophyta will be the subject of the present paper.

As a result of these trips only two species of Chara were collected, one of which, viz. C. fibrosa , was new for the area under discussion. No representative of the other Charophyta genera was detected. Though several species are recorded from the north coast of South America (cf. Braun, 1858; Braun & Nordstedt, 1882), so little is known of the Charophyta of the Netherlands West Indian islands that it is worth publishing these few notes. Moreover, a number of ecological data were gathered, which are enumerated at the same time.

 

Date
1942
Data type
Scientific article
Theme
Research and monitoring
Geographic location
Aruba
Bonaire
Curacao

Special Edition: Transboundary Species

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.

 

Date
2019
Data type
Media
Theme
Education and outreach
Research and monitoring
Geographic location
Aruba
Bonaire
Curacao
Saba
Saba bank
St. Eustatius
St. Maarten
Author

Identification cards for common algae on Bonaire

Macroalgae on Bonaire
Macroalgae are large algae, also called seaweeds, that are typically divided in three major groups: red macroalgae (Rhodophyta), brown macroalgae (Phaeophyceae), and green macroalgae (Chlorophyta). Over 250 seaweed species are known from Bonaire. They vary tremendously in shape and color and are found in a range of habitats. They flourish in shallow and deep areas on coral reefs all around the island, in seagrass beds, mangrove forests and in the intertidal.

Macroalgae – important organisms
Macroalgae are mostly notorious as aggressive competitors for space that can overgrow reef corals. However, macroalgae play an important part in all marine ecosystems: they provide food for herbivores, and they stabilize the structure of reefs. Algae are also remarkable in that they are responsible for the high productivity that characterizes coral reefs and seagrass beds.

Identifying macroalgae
These identification cards provide an overview of almost 60 red, brown and green seaweed species that are frequently encountered on Bonaire, to help you explore the macroalgal biodiversity in the marine parks.

Date
2020
Data type
Other resources
Theme
Education and outreach
Geographic location
Bonaire
Image

Early cementation and lithification in intertidal cryptalgal structures, boca jewfish, Bonaire, Netherlands Antilles

On the shore of the Boca Jewfish area of the Lac, Bonaire, N.A., blue-green algae perform a sediment-stabilizing and binding function resulting in a wide variety of cryptalgal structures. The morphology and zonadon of these structures is related to variation in desiccation, sediment influx, water agitation and algal "species." The zunation of intertidal structures consists of stromatolites and oncolites, lithifiod nodules, smooth mat and tufted mat. A cryptalgal crust pavement is found in protected supratidal- areas. In the middle intertidal zone, cryptalgal nodules are lithified during intertidal exposure by pervasive pore-reducing, micritic, high-Mg calcite cement, which is pendent in its distribution around sediment grains. Calcium carbonate cement also occurs as rinds on algal filaments. Precipitated calcium carbonate is found in minor amounts on filaments and mucus within tufted and smooth mats. The preservation potential of the nodules is enhanced by rapid and early cementation. The other structures, not lithified by significant amounts of early cement, have lower preservation potentials. The normal marine salinity of the Lac indicates that growth of cryptalgal structures in fresh, brackish, or hypersaline waters is not essential for their early cementation and lithification.

Date
1979
Data type
Scientific article
Theme
Research and monitoring
Tags
Geographic location
Bonaire
Author

Beta diversity of macroalgal communities around St. Eustatius, Dutch Caribbean

This study provides a baseline of the marine algal flora composition around St. Eustatius, Dutch Caribbean, by describing algal community structure in terms of species richness and beta diversity, and by providing a taxonomically reliable DNA barcode collection. A total of 156 species was found, including 91 that represent new records for St. Eustatius. Subtidal assemblages (126 species) and intertidal assemblages (48 species) showed little overlap. Algae assemblages in seagrass beds differed from those on hard substrates in species composition. In addition, seagrass communities contained a relatively high number of associated green algae species. Artificial substrates (such as shipwrecks) mimicked natural hard substrates in terms of species richness and composition, but missed some key species that characterize natural reef floras. Species accumulation curves and asymptotic species richness estimators show that the expected species richness is higher than the observed number of species, indicating that additional sampling is needed to record rare species. The phylogenetic trees provided in this study identified the presence of cryptic species and fills knowledge gaps in our understanding of Caribbean macroalgae.

Date
2016
Data type
Scientific article
Theme
Research and monitoring
Tags
Geographic location
St. Eustatius

Algal cover and the effects of various nutrient levels on Bonaire's coral reefs

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.

Date
2006
Data type
Other resources
Theme
Research and monitoring
Geographic location
Bonaire

Examining the effect of different grazers on algal biomass

Herbivory drives ecosystem dynamics in both terrestrial and marine habitats, controlling type and biomass of vegetation. In tropical coral reefs, herbivorous fishes and invertebrates feed on benthic macroalgae, resulting in decreased algal biomass and increased hard substratum available for coral growth and recruitment, providing for increased levels of biodiversity. In 1983, the long-spined sea urchin, Diadema antillarum, suffered mass mortality in the Caribbean, resulting in dramatic changes to ecosystem dynamics such as decreased coral cover and increased macroalgal cover. This study aimed to examine the impact of various grazers on algal biomass in areas with and without D. antillarum in Bonaire, Dutch Caribbean, from late February to early April, 2012, using herbivore exclusion cages with varying levels of exclusion. Grazer categories were established based on cage type and proximity to D. antillarum. It was hypothesized that algal biomass would decrease with increased herbivore access. At locations with D. antillarum, there was a general increase in algal biomass with increased exclusion, whereas at locations without D. antillarum, the opposite trend was observed. Algal biomass generally decreased with increased grazer access; however, differences were not statistically significant. Herbivorous fishes removed the highest amount of algae, followed by D. antillarum, and large invertebrates. This study shows the importance of multiple herbivores in maintaining low algal biomass in Bonaire.

This student research was retrieved from Physis: Journal of Marine Science XI (Fall 2012)19: 1-8 from CIEE Bonaire.

Date
2012
Data type
Other resources
Theme
Research and monitoring
Tags
Geographic location
Bonaire
Author