Robyn Laing - Proposal

Prevalence, Characteristics, and Implications of Competition between Algae, Ascidians, and Coral in Finite Reef Patches off the Coast of Isla de la Juventud, Cuba

INTRODUCTION Coral reefs are home to the widest array of biodiversity of any marine ecosystem. They not only provide refuge, substrate, and habitat for numerous aquatic species, but also provide many economic and ecological services to humans, free-of-charge. These services include tourism income, coastline protection from wave energy and erosion, sand generation for the beautiful white beaches of the Caribbean, and of course, production of food (Burke et al., 2004). Such economic benefits and services have been calculated to be annually valued at US$100,000 to US$600,000 per km2 of reef (Constanza et al., 1998). With an estimated 284,300 km2 of reef cover worldwide, this amounts to US$28 billion to US$170 billion annually (UNEP-WCMC, 2006). Moreover, in addition to these economic benefits there are also potential medicinal benefits, with the immense biodiversity provided by coral reefs being utilized in the formation of potentially life-saving pharmaceuticals and drugs (Bernstein et al., 2008). Given such abundant benefits, and the fact that over 1/3 of the world’s population relies on coral reefs for coastal protection and food generation, it is of great interest and importance to study the mechanisms and reasons behind the dramatic decline in the health and extent of coral reefs that has occurred over the last century (UNEP-WCMC, 2006). Over 30% of the world’s coral reefs are currently listed as “seriously damaged” (Burke et al., 2004), and in many studies it has been found that such dramatic coral reef declines have largely been due to anthropogenic factors (Mora, 2008, De’ath et al., 2009, Aronson et al., 2006). These factors include overfishing, pollution, nutrient loading, coastal development, tourism, and recreational diving (Tilot et al., 2008). It has been suggested that such anthropogenic factors contribute to coral reef decline because they result in an increase in damaging natural events and processes, such as eutrophication, increased ocean water temperatures, coral bleaching, and increased instances of coral disease (Mora, 2008). However, though such anthropogenic factors do play a large role in the decline of coral reefs, the effects of other factors, such as competitive interrelation between marine organisms, has not been readily studied (Titlyanov et al., 2008). This competition may exist between species of coral and algae, as well as between coral and other organisms, such as a variety of ascidians, like the overgrowing tunicate Trididemnum solidum, and can result in decreased coral cover (Hernandez-Zanuy et al., 2001). Furthermore, though the effects of many anthropogenic factors have been readily studied in the Caribbean, studies observing the effects of increased competitive interrelation, particularly between coral and ascidians, have not been as prevalent here (Hernandez-Zanuy et al., 2001). Given that the Caribbean has had an average loss of 40% coral cover since the late 1970s (Gardner et al., 2003) and supports 25 million tourists a year and over 116 million people living within 100km of the coast (Burke et al., 2004), it is of great interest to study all possible causes of reef degradation and decline in this area. In particular, the ecological scale of competition by algae and ascidians, as well as details relating to habitat, patterns of co-occurrence, and relationship between coral morphology and ascidian and algal overgrowth is largely unknown (Shenkar et al., 2008) and should therefore be studied.

HYPOTHESIS As mentioned, it has been found that a large and significant decline in the health and extent of coral cover has occurred over the last decade (UNEP-WCMC, 2006). In addition, it has also been found that algal and ascidian species are more prevalent on damaged or destroyed reefs (Tityanov et al., 2008), and that anthropogenic activity creates favourable conditions for the growth of these species over coral (Shenkar et al., 2008). It has also been found that algal and ascidian species compete for space with reef-building corals, and thus could hamper the full restoration and re-growth of corals after damage has occurred (Shenkar et al., 2008). As a result, it is hypothesized that increased prevalence and more rapid growth of algal and ascidian species will be observed in areas where damaged coral is abundant. Furthermore, given the fact that it has been suggested that algal colonization may not be as detrimental to the re-growth of coral as ascidian colonization (Tityanov et al., 2008), it is further hypothesized that reef patches with a higher percentage of ascidian colonization in comparison to algal colonization will exhibit less coral cover overall. APPROACH In order to test the hypothesis it will have to be determined (a) whether algal and ascidian growth exists in areas of coral damage, (b) whether algal and ascidian growth exists in areas of healthy coral, (c) whether there is increased speed in algal and ascidian growth in areas of coral damage, (d) whether there is increased algal and ascidian cover in areas of coral damage, (e) whether there is decreased coral cover in areas with algal and ascidian growth and (f) whether reef patches with higher ascidian cover versus algal cover exhibit less coral cover overall. Therefore, the approach of this study will be correlational in order to determine the relationships between coral morphology and ascidian and algal growth, as well as whether ascidian growth correlates to lower coral cover than algal growth. This approach will require that the following data be collected:      

Amount of algal and ascidian cover on damaged reef patches o Divided into percent algal cover and percent ascidian cover Amount of algal and ascidian cover on healthy reef patches o Divided into percent algal cover and percent ascidian cover Rate of algal and ascidian growth on damaged reef patches Rate of algal and ascidian growth on healthy reef patches Amount of coral cover on reefs where algal and ascidian growth does not occur Amount of coral cover on reefs where algal and ascidian growth occurs o Percent coral cover on reefs where ascidian cover is greater than algal cover o Percent coral cover on reefs where algal cover is greater than ascidian cover

OBSERVATIONAL DESIGN 1. Site Selection In order to obtain an adequate sample size and a sufficient amount of statistical replicates, 25 reef patches will be randomly chosen. These reef patches will be selected by randomly generating 25 numbers from 1-30, with each number corresponding to a selected reef patch based on previous studies. Among each selected site three 1m x 1m quadrants will be randomly placed in areas with and without coral damage as well as in areas with and without algal and ascidian growth. If damage of coral is a factor in the growth of algae and ascidians, and ascidian and algae growth is a factor in coral cover, differences in cover should be observed. 2. Amount of Ascidian and Algal Cover The amount of ascidian and algal cover will be determined both as a percentage of the surface area of the quadrant as well as the total volume occupied in space. The percentage will be determined by measuring the length and width of the ascidian and algal cover and dividing this value by the area of the quadrant (1m2). The volume will be determined by measuring the average height and multiplying this value by the area of cover. The results will be recorded in tables similar to Table 1, with data from quadrants containing damaged coral being recorded in one table and data from quadrants containing healthy coral recorded in another table. 2

Table 1: Ascidian and algal cover in randomly placed 1m quadrants on randomly selected reef patches

COVER Ascidian (TOTAL) Reef Patch # Quadrant # Species Algal (TOTAL) Reef Patch # Quadrant # Species

Length (m)

Width (m)

Area (m2)

Percent (%)

Height (m)

Volume (m3)

3. Amount of Coral Cover The amount of coral cover will also be determined both as a percentage of the surface area of the quadrant as well as the total volume occupied in space. The percentage will be determined by measuring the length and width of the coral cover and dividing this value by the area of the quadrant (1m2). The volume will be determined by measuring the average height and multiplying this value by the area of cover. The results will be recorded in tables similar to Table 1, but with Ascidian/Algal cover changed to Coral cover.

4. Rate of Algal and Ascidian Growth The rate of growth will be determined by randomly selecting two algal and ascidian growths in the first selected reef patch. One algal and one ascidian growth will be randomly selected from a damaged coral area within the reef patch, and the other algal and ascidian growth will be randomly selected from an undamaged coral area within the reef patch. The rate of each growth will be measured daily by measuring the amount of cover (see 2) in terms of area and volume. The rate will then be calculated by using these values to determine the average daily increase in area and volume of the algal and ascidian cover in both the damaged and undamaged coral areas. The results will be recorded in tables similar to Table 2, with one table designated for data pertaining to growth in damaged coral areas and one table designated for data pertaining to growth in undamaged coral areas. 2

3

Table 2: Ascidian and algal growth in a randomly selected reef patch. Recorded in terms of area (m ) and volume (m ) per day

GROWTH

Day 1

Day 2

Day 3

Day 4

Day 5

etc...

Ascidian Length (m) Width (m Area (m2) Height (m) Volume (m3) Algal Length (m) Width (m Area (m2) Height (m) Volume (m3)

MATERIALS NEEDED         

SCUBA equipment – mask, snorkel, fins, wetsuit, BCD, dive belt, regulator, air tank, dive watch Three 1m x 1m quadrants – PVC pipes, elbow joints, string Measuring tape Underwater plastic slates and pencils to record observations Erasers and fine-grained sandpaper to clean slates after each dive Coral of the Caribbean Underwater Identification Key Ascidians of the Caribbean Underwater Identification Key Algae of the Caribbean Underwater Identification Key Copy of tables to record and keep track of daily data

REFERENCES

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