Species richness

Abstract:

Understanding the patterns and processes that govern the functional structuring of communities along spatial scales is still a challenge in community ecology. Functional diversity is the result of the action of abiotic and biotic filters that regulate the presence and contribution of functional attributes inside the assemblages. Large-scale studies demonstrate that reef fish fauna has a high degree of functional redundancy, where the addition of species does not normally result in new functions in local assemblages. However, niche theory predicts that species tend not to overlap in resource use, a pattern that can be exacerbated at small scales. In this context, the aim of this study is to investigate how the functional structure of reef fish assemblages respond to area increase in three locations in the western Atlantic Ocean subject to a wide gradient of species richness: Curaçao, Abrolhos and Atol das Rocas. More specifically, the relationships between the indices of functional richness (FRic), functional evenness (FEve) and area were evaluated. Based on niche theories and efficient use of resources, we hypothesized that as area increases, new niches become available, and therefore new species are sampled. Likewise, it is expected that functional richness will increase as the sample area increases. On the other hand, evenness may decrease, since larger areas can accommodate more functionally similar species and concentrate greater accumulations of functional entities in certain areas of the functional space, decreasing the FEve. For this purpose, species occurrence data were gathered from checklists and occurrence and abundance data from 40 m² visual censuses. Species were classified into eight functional attributes. For each metric, FRic and FEve accumulation curves were constructed using an extension of the Gower dissimilarity matrix and Principal Coordinate Analysis (PCoA). Functional indices were calculated from randomization of sample units (visual censuses) and contrasted with null models. We found that increases in the sample area lead to an increase of FRic and a decline of FEve, regardless of local species richness. Also, small sample areas are characterized by high FEve (i.e., functional entities are more evenly distributed in the functional space). Regardless of the species richness, the functional spaces are relatively similar between the three locations, suggesting that even isolated reefs have communities that present a minimal functional structure to maintain the functioning of the ecosystem. These patterns may be related to the optimization of resource use in isolated and poorly connected areas, a mechanism to reduce local competition. The combination of limiting similarity and the best use of available resources result in a high functional equitability ? when the functional entities are more evenly distributed in space. These processes, therefore, may have shaped the functional structure of communities in isolated reef systems sampled.

https://repositorio.ufsc.br/handle/123456789/242634

Abstract

Invasions by non-native plant species are widely recognized as a major driver of biodiversity loss. Globally, (sub-)tropical islands form important components of biodiversity hotspots, while being particularly susceptible to invasions by plants in general and vines in particular. We studied the impact of the invasive vine A. leptopus on the diversity and structure of recipient plant communities on the northern Caribbean island St. Eustatius. We used a paired-plot design to study differences in species richness, evenness and community structure under A. leptopus-invaded and uninvaded conditions. Community structure was studied through species co-occurrence patterns. We found that in plots invaded by A. leptopus, species richness was 40–50% lower, and these plots also exhibited lower evenness. The magnitude of these negative impacts increased with increasing cover of A. leptopus. Invaded plots also showed higher degrees of homogeneity in species composition. Species co-occurrence patterns indicated that plant communities in uninvaded plots were characterized by segregation, whereas recipient plant communities in invaded plots exhibited random cooccurrence patterns. These observations suggest that invasion of A. leptopus is not only associated with reduced species richness and evenness of recipient communities in invaded sites, but also with a community disassembly process that may reduce diversity between sites. Given that A. leptopus is a successful invader of (sub-)tropical islands around the globe, these impacts on plant community structure highlight that this invasive species could be a particular conservation concern for these systems.

Biodiversity of coral reef fish species is often related to the structural complexity and diversity of their habitats. This study explores the relationship between fish species richness, habitat diversity (substrate diversity) and habitat complexity (rugosity). Habitat diversity and topographic measures were used to predict reef fish diversity. It was hypothesized that high fish species diversity would show a positive correlation with greater habitat structure, which includes habitat diversity and topographic complexity. Fish species richness was determined at six dive sites in Bonaire, N.A. (Karpata, Andrea II, Cliff, Windsock, Angel City, and Red Slave) using data from 20 randomly chosen expert-level surveys provided by Reef Educational Environmental Foundation (REEF) for 2004 – 2009. Preliminary analysis of REEF data was used to select sites with high and relatively low fish species richness to make comparisons with the habitat structural complexity measurements (substrate diversity and rugosity). Substrate diversity and habitat complexity were measured using a 10 m transect randomly placed at 4 depths (2, 6, 12, and 18 m) at each site. Substrate diversity was determined by measuring the percent cover of the different substrates and then using the Shannon Diversity Index to determine H’. The rugosity of the sample area was measured by fitting a lead line to the reef at each of the determined depths. Overall results suggested that topographical complexity (rugosity) was not related to high fish species richness at dive sites on Bonaire. There was a weak positive correlation between H’ and fish species richness on the reef slope and a weak negative relationship between H’ and fish species richness on the reef flat. The results provide evidence that there are more factors to consider when explaining fish species richness on coral reefs than the structural complexity of the habitat at the scale of this study.

This student research was retrieved from Physis: Journal of Marine Science VI (Fall 2009)19: 66-72 from CIEE Bonaire.

Cleaner shrimp are commonly found throughout Caribbean coral reefs and can effectively reduce parasite loads on reef fish resulting in increased fitness of local reef fish populations. The marine cleaner shrimp, Periclemenes pedersoni, most commonly inhabits two coral reef anemones, Condylactis gigantea or Bartholomea annulata, which have different distribution patterns on reefs. C. gigantea resides on hard or rocky substrates with greater relief, whereas B. annulata lives on muddy, sandy substrates or crevices with less relief. Past studies have been done on cleaning by P. pedersoni, yet no research has been done on the effects the differing host anemones may have on cleaning interactions. Using 12 min observation periods between 13:00 -17:00 h on the fringing reef in Bonaire, number of P. pedersoni shrimp, number of clients, species of clients, and time cleaned per client were recorded for C. gigantea and B. annulata anemone cleaning stations. When compared to B. annulata, C. gigantea had significantly more P. pedersoni shrimp, which cleaned a significantly greater number of client fishes. Greater species richness of clients was observed visiting C. gigantea than B. annulata cleaning stations, however there was no difference in time spent cleaning per client. Although protected in Bonaire, aquarium trade collection of C. gigantea throughout the rest of the Caribbean may result in an overall reduction in the number of cleaning interactions occurring on the reef, potentially having detrimental effects on the health of local fish populations.

This student research was retrieved from Physis: Journal of Marine Science IX (Spring 2011)19: 31-37 from CIEE Bonaire.

Coral reefs have existed for thousands of years and are currently subjected to many threats. Coral disease is of particular concern because of its increasing prevalence; because they reduce coral cover, diseases are likely to affect fish assemblages. This study looks at the factors of coral disease and fish species richness on Bonaire, Dutch Caribbean. The study tests the hypotheses that (1) the amount of coral disease present in Bonaire has increased since 2007 and (2) the species richness of fish assemblages decreases with increasing presence of coral disease. Coral disease prevalence and live coral cover was assessed using an adaptation of the AGRRA benthic methodology by laying 10 m transects at depths of 10 and 12.5 m at Cliff and Windsock, areas that are closed and opened to fishing respectively. In addition, fish species richness was assessed using the roving diver technique by REEF. There was a significant difference between coral disease, as well as live coral cover, between sites and years. Species richness had a significant weak but not significant correlation with coral disease and live coral cover. However, no significant difference was found in the fish species richness between sites or between years.

This student research was retrieved from Physis: Journal of Marine Science X (Fall 2011)19: 40-46 from CIEE Bonaire.

Coral reefs around the world are experiencing high levels of degradation due to temperature changes, increased nutrients and destructive fishing techniques. For example, where there were once large thickets of the branching coral Acropora cervicornis along the coasts of Bonaire, Dutch Caribbean, there is now sand and dead coral. Loss of an entire highly complex habitat has likely altered the local reef fish community. Artificial reefs have been used in the past to test hypotheses about structural complexity and its effects on reef fish communities. However, no studies have sought to discover if artificial reef structures modeled after A. cervicornis would support reef fishes found in the natural branching coral colonies by mimicking the structural complexity provided by the coral. To answer this question, four patches of artificial A. cervicornis were constructed and placed near the reef crest on the leeward side of Bonaire, Dutch Caribbean. Natural thickets of A. cervicornis were used to compare differences in fish species richness, diversity and density. Artificial reef structures were found to support higher diversity but lower abundance of fish. There was no significant difference in species richness between the natural and artificial reef stands. Overall, the artificial reef structures were able to provide some shelter to certain fish species, but were not able to support the fish community that is supported by natural stands of A. cervicornis.

This student research was retrieved from Physis: Journal of Marine Science X (Fall 2011)19: 21-27 from CIEE Bonaire.

The biodiversity of coral reefs will decline as the global degradation of reefs continues, pushing the science of restoration techniques such as the utilization of artificial reefs, to the forefront of coral reef ecology. Artificial reefs provide shelter and habitat through design features such as topographic complexity, substrate diversity, refuge hole size, vertical relief, and percentage live coral cover. These elements have been manipulated to study the relationship between design and fish community response. This study examines the relationship between hole size in artificial reef units (ARUs) and species richness and abundance of coral reef fish at a study site on Bonaire, Dutch Caribbean. Four types of ARUs were constructed including units with no holes, small holes, large holes and a combination of small and large holes. Various fish and invertebrate species utilized ARUs for grazing, benthic egg laying, protection and hunting. There was no difference in fish density or species richness among the four ARU types. However, differences in species composition among the four ARU types were found. The smaller, benthic fish were more prevalent at the small hole ARU, while the larger, territorial fish were found utilizing the large hole and no hole ARUs more often. Mixed hole ARUs exhibited a compilation of both small and large fish. Since there are differences in community composition, specialized artificial reef designs could possibly be used to enhance particular species that are important to maintain community structure of degraded reefs.

This student research was retrieved from Physis: Journal of Marine Science X (Fall 2011)19: 1-10 from CIEE Bonaire.

Coral reef environments exhibit numerous ecological interactions between different organisms. The habitat structure of a healthy coral reef is composed of many different coral species, with various fish species inhabiting the reef. Coral reef studies often focus on a large spatial scale rather than smaller local scale environments within the reef. The objective of this study was to compare fish populations associated with the microhabitat surrounding individual coral heads of two different species. The purpose of this study was to determine if there were differences in fish abundance, fish species richness, and fish diversity between two massive stony corals, Diploria strigosa and Orbicella annularis. These two corals are common on many Caribbean reefs but are morphologically different; therefore, it was hypothesized that they would show differences between their associated fish assemblages. By conducting fish count observations on both D. strigosa and O. annularis, I was able to compare means between the coral associated fish populations using statistical tests. No statistically significant differences were found between these two coral species for mean fish abundance, species richness, or diversity. One possible explanation is that the larger scale reef environment and processes may have a significant effect on local fish populations found on individual coral heads. By studying the microhabitats of coral species and the associated fish assemblages, we can gain a better understanding of fish population dynamics of coral reefs across larger ecological scales—both regionally and globally

This student research was retrieved from Physis: Journal of Marine Science XVIII (Fall 2015)19: 61-69 from CIEE Bonaire.

Excess nutrients as a result of agricultural, urban, and industrial runoff are major causes to increases in plankton. Coral reefs are nutrient poor environments to begin with; therefore any increase in inorganic nutrients could potentially alter the balance of these ecosystems. Bonaire is suffering from nutrient input in the coastal waters and said trends are expected to increase in subsequent years. Zooplankton diversity and species richness, photosynthetic pigments, water properties and nutrients were measured at two different sites in Kralendijk, Bonaire. The most common taxonomic groups at each site were copepods and siphonophores. The difference in mean turbidity between the two sites was statistically significant (ttest; n = 14; p = 0.002). Excessively turbid water can be explained by an increased plankton population but also by sediment runoff from events such as coastal construction. A possible trend was found between number of zooplankton individuals, chlorophyll a, turbidity, and ammonia nitrogen concentration. This trend could indicate abnormal amounts of runoff entering the waters surrounding Bonaire. Not only is marine management necessary, but also an additional terrestrial aspect to monitor in the form of wastewater and watershed management. Zooplankton taxonomic groups identified during this study could be used as indicators of reef ecosystem health, reproduction success of organisms with planktonic larvae, or predator-prey impact studies such as with pelagic predators of zooplankton. Overall, this study shows important indicators of management for urban areas on Bonaire, but could also contribute to future ecological studies on zooplankton population dynamics around the Caribbean.

This student research was retrieved from Physis: Journal of Marine Science XVIII (Fall 2015)19: 1-9 from CIEE Bonaire.

Aim

Coral assemblages on Caribbean reefs have largely been considered to be biogeographically homogeneous at a regional scale. We reassess this in three taxa (corals, sponges and octocorals) using three community attributes with increasing levels of information (species richness, composition and relative abundance) across hierarchical spatial scales, and identify the key environmental drivers associated with this variation.

Location

Caribbean Basin.

Methods

We assessed reefs along 546 transects positioned within the same forereef habitat (Orbicella reef) in 11 countries, using a consistent methodology and surveyors. Spatial variability in richness, composition and relative abundance was assessed at four hierarchical spatial scales – transects (metres), sites (kilometres), areas (tens of kilometres) and regions (hundreds of kilometres) – using permutational multivariate analysis of variance (PERMANOVA). The relevance of contemporary environmental factors in explaining the observed spatial patterns was also assessed using PERMANOVA.

Results

Consistent with previous studies, species richness of coral assemblages, commonly the focus of biogeographical studies, showed little variance at large spatial scales. In contrast, species composition and relative abundance showed significant variability at regional scales. Coral, sponge and octocoral assemblages each varied independently across spatial scales. Rugosity and wave exposure were key drivers of the composition and relative abundance of coral and octocoral assemblages.

Main conclusions

Caribbean reef assemblages exhibit considerable biogeographical variability at broad spatial scales (hundreds of kilometres) when more responsive community attributes were used. However, the high degree of variability within sites (kilometres) highlights the relevance of local ecological drivers such as rugosity and wave exposure in structuring assemblages. The high levels of within-site variability that is not explained by environmental variables may suggest a previously unrealized contribution of anthropogenic disturbance operating at local scales throughout the region.