A review of the diversity and impact of invasive non-native species in tropical marine ecosystems

Tropical marine ecosystems are biologically diverse and economically invaluable. However, they are severely threatened from impacts associated with climate change coupled with localized and regional stressors, such as pollution and overfishing. Non-native species (sometimes referred to as ‘alien’ species) are another major threat facing these ecosystems, although rarely discussed and overshadowed by the other stressors mentioned above. NNS can be introduced accidentally (for example via shipping activities) and/or sometimes intentionally (for aquaculture or by hobbyists). Understanding the extent of the impacts NNS have on native flora and fauna often remains challenging, along with ascertaining when the species in question actually became ‘invasive’. Here we review the status of this threat across key tropical marine ecosystems such as coral reefs, algae meadows, mangroves, and seagrass beds. We aim to provide a baseline of where invasive NNS can be found, when they are thought to have been introduced and what impact they are thought to be having on the native ecosystems they now inhabit. In the appended material we provide a comprehensive list of NNS covering key groups such as macroalgae, sponges, seagrasses and mangroves, anthozoans, bryozoans, ascidians, fishes, and crustaceans.N

Observations on the reproduction of <i>Acropora</i> corals along the Tuticorin coast of the Gulf of Mannar, Southeastern India

219-226Pattern of reproduction was studied in Acropora species along Tuticorin coast in the Gulf of Mannar from 2006-2008. Extensive surveys were conducted to monitor reproductive maturity and the timing of spawning. Gametes were observed from January with colonies releasing gametes by the end of March. Acropora cytherea showed immature colonies in January (48-79%) and February (56-76%) and mature colonies in March (36-86%). Likewise, the other species of Acropora examined showed 50-75% of immature colonies in January and an increase of 10-20% of immature colonies in February, and matured in March. The average percentage of mature colonies in March was as follows, A. formosa 47-76%, A. valenciennesi 50-81%, A. intermedia 50-81%, A. nobilis 25-82%, A. micropthalma 56-83%, A. hemprichi 39-83%, A. hyacinthus 33-100%, A. corymbosa 59-65%. Spawning was observed in A. cytherea on 24 March 2006, 10 days after full moon; 28 March in 2007, 5 days prior to full moon; and 8 March 2008, 1 day after new moon. Approximately 30,000 egg and sperm bundles were observed in 1 litre of water and each bundle had 20-25 eggs in A. cytherea. Environmental parameters, especially rise in temperature at the end of March was believed to play lead role in coral spawning

Under water visual census of reef fishes in Tuticorin group of islands, Gulf of Mannar, Southeastern India

1585-1597Reef fishes are integral part of coral reef ecosystem as they play major role in ecological balance. Visual census of fish assemblages on coral reefs in the vicinity of four islands in Tuticorin group, Gulf of Mannar, Southeast coast of India was conducted between August 2011 and November 2012. Under water data collection on reef fish abundance and diversity was done by following belt transect method involving scuba diving. A total of 78 species from 24 families were recorded during the study period. . Kariyachalli Island was recorded the highest density and diversity of reef fishes (64 species) among the four islands and this dominance is corroborated to the comparatively higher live coral cover (46.61%). The study reveals that habitat complexity determines the abundance and diversity of reef fishes in a reef area. Presently, anthropogenic and natural factors threaten coral reefs and protection of reef habitat is inevitable for the survival and existence of reef fishes and ultimately the livelihood of the dependant people

Study on the status of corals in Palk Bay, Southeast coast of India during 2007-2013

1449-1462Present study consists the status of corals in Palk Bay, conducted during 2007-2013. Corals are distributed in four sites (Mandapam north, Pamban, Thangachimadam and Olakuda) in Southern Palk Bay. The overall live coral cover was 30.78, 29.64 and 28.24% respectively during July 2007, September 2009 and April 2013. A sharp decrease in the live coral cover was observed in Mandapam north from 34.18 to 22.62% during the study period and an increase of algae from 14.88 to 31.52% was also recorded. The overall disease prevalence increased from 15.28% to 17.32% between 2009 and 2013. A complete stretch of Acropora cytherea in Mandapam north was dead because of the black band disease and the area is now dominated by macro algae. The other anthropogenic factors including destructive fishing practices, cultivation of exotic seaweed, Kappaphycus alvarezii, and elevated temperature pose threat to corals in Palk bay

First observation of coral spawning slicks near Kudankulam coastal area, Southern Gulf of Mannar, Tamil Nadu

742-743Coral spawning slicks were noticed for the first time near Kudankulam coastal area, Southern Gulf of Mannar, Tamil Nadu. Timing of coral spawning in Gulf of Mannar has been reported to be March every year. Thus this record aligns with the previous record from Tuticorin coastal region and a recent report from Lakshadweep Islands. Linking the sighting of numerous coral recruits and the current sighting of spawning slicks in this area it is believed that corals in Kudankulam coastal area, though in patches are sexually mature and actively participate in sexual reproduction

Unscientific diving practices for livelihood resulting in loss of human lives in Tuticorin coast, Southeastern India

924-92

Reproductive success of restored coral colonies in Vaan Island, Gulf of Mannar, Southeastern India

589-598<span style="font-size:9.0pt; font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" mso-bidi-font-family:mangal;mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:hi"="" lang="EN-US">Present study consists reproductive behaviors of natural and transplanted acroporan corals in Vaan Island of the Gulf of Mannar. Single reproductive season per year and reproductive synchrony have been observed during the study period between 2008 and 2010 among the monitored Acropora species in both natural and transplanted colonies. Studies on the gametogenic cycle in three species, Acropora intermedia, A. nobilis and A. cytherea showed a single annual cycle of gametogenesis. Patterns of oogenesis, spermatogenesis and fecundity were almost similar between the three species and between natural and restored colonies. Multi-specific synchronous spawning was observed among the acroporans from both natural and restored colonies during March in all the study years. It was obvious that restored corals involve in the sexual reproduction effectively in Vaan Island exactly as the natural corals. Hence restoration through fragment transplantation is a successful option to employ in any degraded reef. </span

Status of Alcyonacean corals along Tuticorin coast of Gulf of Mannar, Southeastern India

666-675In this study, the assessment of alcyonaceans was conducted in Tuticorin coast of the Gulf of Mannar during the period between 2010 and 2012 in 5 locations; Vaan, Koswari, Kariyachalli and Vilanguchalli islands and mainland Punnakayal patch reef. Average alcyonacean coral cover in Tuticorin coast was 6.76% during 2011-12 which was 5.61% during 2010-2011. Percentage cover of alcyonacean corals increased in all the study locations; Kariyachalli 12.04 to 13.96%; Vilanguchalli 8.94 to 10.23%; Koswari 1.6 to 3.69; Vaan 0.53 to 0.72; mainland Punnakayal patch reef 4.95 to 5.21% was documented. In total, 15 species from 7 genera were recorded during the study period. Though anthropogenic threats in Tuticorin coast are comparatively high, the abundance of alcyonacean corals has increased considerably showing their resilience and adaptability. </span

Coral diseases are major contributors to coral mortality in Shingle Island, Gulf of Mannar, southeastern India

The present study reports coral mortality, driven primarily by coral diseases, around Shingle Island, Gulf of Mannar (GOM), Indian Ocean. In total, 2910 colonies were permanently monitored to assess the incidence of coral diseases and consequent mortality for 2 yr. Four types of lesions consistent with white band disease (WBD), black disease (BD), white plaque disease (WPD), and pink spot disease (PSD) were recorded from 4 coral genera: Montipora, Pocillopora, Acropora, and Porites. Porites were affected by 2 disease types, while the other 3 genera were affected by only 1 disease type. Overall disease prevalence increased from 8% (n = 233 colonies) to 41.9% (n = 1219) over the 2 yr study period. BD caused an unprecedented 100% mortality in Pocillopora, followed by 20.4 and 13.1% mortality from WBD in Montipora and Acropora, respectively. Mean disease progression rates of 0.8 +/- 1.0 and 0.6 +/- 0.5 cm mo(-1) over live coral colonies were observed for BD and WBD. Significant correlations between temperature and disease progression were observed for BD (r = 0.86, R-2 = 0.75, p < 0.001) and WBD (R-2 = 0.76, p < 0.001). This study revealed the increasing trend of disease prevalence and progression of disease over live coral in a relatively limited study area; further study should investigate the status of the entire coral reef in the GOM and the role of diseases in reef dynamics