Abundance of reef fish and the condition of Paraviwella reef, Tangalle, South, Sri Lanka (original) (raw)
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2015
Shallow reef habitats dominated with living corals is relatively accessible all times of the day and could be useful to consider as a natural mesocosm. This study was conducted at Paraviwella near shore reef patch, Tangalle, Southern Sri Lanka (6° 01’ 17.07” N, 80° 48’ 01.21” E) from 25 April 2014 to 10 September 2014 to examine the current status of the substratum composition. Line Intercept Transects (LITs) method was used for benthic composition study (number of transects = 6, length = 25m and area 3500 m). Temperature (T), Salinity (S), Turbidity (Tb) and Dissolved Oxygen (DO) were measured in sea water collected from transect locations. Results disclosed that sea water quality at Paraviwella reef were within the suitable condition for growth of corals and other associated organisms (T=29 ± 1°C, D=54 ± 17 cm, S=34 ± 1ppt, Tb=3 ± 0.6 NTU, DO=8.6 ± 1 ppm). Transect study showed that living corals (64.7 ± 18.9%) and algae (19.2 ± 13.4%) were dominant life forms represented by highe...
The Dynamics of Benthic Algae among Herbivorous Coral Reef Fishes
2013
This study was carried out to determine the extent of herbivores reef fish composition that can control the distribution of algae. A total of three 50 m transect lines placed at three different locations based on domination of algae functional groups. The study was conducted in Barranglompo Island, Makassar, South Sulawesi, Indonesia in March-June, 2012. The abundance and biomass of fish herbivore was observed through underwater visual census. All species were recorded to number and class size and grouped into their functional groups. The benthic algae cover was measured using the quadrant method in transect lines. Their distributions were observed periodically to determine the extent of the effects of grazing reef fish herbivore on benthic algae. The results showed that the epilithic algal matrix tend to correlate negatively with fish herbivore scrapers while the composition of herbivore reef fish can control the existence of algae distribution within the coral reef resilience. How...
2020
Corals are found in tropical and sub-tropical world’s oceans. Corals are the most diversified, economically, and ecologically valuable ecosystems. Reef ecosystem covers 0.1% area of the world and supports 25% of ocean life, including fish, crustaceans, mammals, sponges, and echinoderms. Corals are also known as Rainforests of the Sea’ because of the native biodiversity. Coral reefs provide economic, social, cultural, and ecosystem services. Despite providing immense ecosystem services, corals are degraded to a great extent due to climate change, anthropogenic threats, Coastal development, overfishing, and destructive fishing practices. This magnificent creature of nature needs to be protected by adopting management and conservation strategies recommended by national and international authorities. Some advanced management methods like satellite-based study (mapping, monitoring) and coral gardening adaptation are essential for obtaining maximum benefits out of the reefs ecosystem with...
Coral reef grazer-benthos dynamics complicated by invasive algae in a small marine reserve OPEN
Blooms of alien invasive marine algae have become common, greatly altering the health and stability of nearshore marine ecosystems. Concurrently, herbivorous fishes have been severely overfished in many locations worldwide, contributing to increases in macroalgal cover. We used a multi-pronged, interdisciplinary approach to test if higher biomass of herbivorous fishes inside a no-take marine reserve makes this area more resistant to invasive algal overgrowth. Over a two year time period, we (1) compared fish biomass and algal cover between two fished and one unfished patch reef in Hawai'i, (2) used acoustic telemetry to determine fidelity of herbivorous fishes to the unfished reef, and (3) used metabarcoding and next-generation sequencing to determine diet composition of herbivorous fishes. Herbivore fish biomass was significantly higher in the marine reserve compared to adjacent fished reefs, whereas invasive algal cover differed by species. Herbivorous fish movements were largely confined to the unfished patch reef where they were captured. Diet analysis indicated that the consumption of invasive algae varied among fish species, with a high prevalence of comparatively rare native algal species. Together these findings demonstrate that the contribution of herbivores to coral reef resilience, via resistance to invasive algae invasion, is complex and species-specific. Herbivorous fishes and sea urchins are primarily responsible for the high grazing intensity found in healthy coral reef ecosystems 1–3. This intense grazing pressure has a large influence on the distribution of algae on coral reefs, with macroalgae generally rare in reef zones with the highest grazing pressure 2,4,5. Although there has been some debate regarding the mechanisms and causality of competition between algae and corals 6 high algal biomass has been shown to have a negative effect on coral health 7–9. Based on their role in algal removal, herbivorous fishes are considered to promote reef resilience and assist in reef recovery to coral dominated states after a disturbance 10–12. Over the past several decades, blooms of both indigenous and introduced marine algae have become common on coral reefs, greatly altering the health and stability of nearshore ecosystems 10,13. On reefs subjected to anthropogenic disturbances such as increased terrestrial nutrient inputs or the removal of grazers by overfishing, algal growth rates may exceed grazing rates, resulting in overgrowth of hard corals and other non-mobile ben-thic invertebrates, and suppression of coral recruitment 14–16. Herbivorous fishes, particularly large parrotfishes and surgeonfishes, have been severely overfished in many locations/regions and reduction in these grazers has been thought to contribute to increases in macroalgae and subsequent decreases in coral cover 17–19. Introduced species of macroalgae are often not subject to ecological controls that normally limit abundance in their native range, such as high grazing pressure from native herbivores, allowing them to become invasive 20,21 and accelerate coral-algal phase shifts on coral reefs. Herbivorous fishes play an important role in promoting resilience and supporting coral recovery, and tend to have small home ranges, suggesting that relatively small-scale (1–10 s km) variation in their abundance will contribute to local changes in rates of reef recovery 22,23. Therefore, local-scale management measures that decrease fishing mortality and increase the abundance and size of herbivorous fishes, such as marine reserves, are expected to play a significant role in supporting recovery and resilience of coral reef ecosystems 24,25. The extent to which different species of herbivorous fishes control macroalgae and promote coral recovery will also depend on their functional role and the algae upon which they graze 26. Herbivorous fish species tend to be selective in their