Ocean and Coastal Eco System

 Ocean and coastal Ecosystems 

 Coastal habitats of Asia are diverse, and the impacts of 

    climate change, including rising temperatures, ocean 

    acidification and SLR, are known to affect the services and 

    livelihoods of the people depending on them. 

   The risk of irreversible loss of many marine and coastal 

    ecosystems increases with global warming, especially at 2C 

    or more high confidence (IPCC, 2018 ) 

   In the South China Sea, coral growth and sea surface 

    temperature ( SST) have shown regional long-term trends 

    and inter-decadal variations, while coral growth is 

    predicted to decline by the end of this century( Yan etal 

    ,2019) 

 

   Only 7.5% of the southern Persian Gulf basin's coral cover 

    was present on average in 2018. As the most vulnerable 

    taxa had already been eliminated by prior bleaching 

    events, this mass mortality did not result in significant 

    changes in the community composition. 

   An exception was the already rare Acropora spp. which 

    were locally extirpated in summer 2017( Burt et al. , 

    2019.)During (2008-2011) also the coral communities of 

    Musandam and Oman showed changes depending on the 

    stress-tolerance levels of the species and the local 

    environmental disturbance level (Bento etal.,  2016). 

   The health and resilience of corals have been found to be 

    associated with beneficial microorganisms of coral BMC 

    which alter during environmental stress. Increasing 

  seawater temperatures have been found to affect the 

  functioning of the symbiotic algae of corals (Lough etal. , 

  2018 Gong etal  2019 ) and its bacterial consortia leading 

  to coral bleaching and mortality (Bourne etal. , 2016 

  Peixoto etal. , 2017 Bernasconi etal. , 2019( Motone etal. , 

  2020). 

 Coral reefs were found to be affected differentially during 

  bleaching episodes, and those species which survived had 

  more stress-tolerant symbionts and higher tolerance to 

  thermal changes( Majumdar etal. , 2018 Thinesh etal. 

  ,2019 van der Zande etal. , 2020). 

 Rare thermally tolerant algae and host species-specific 

  algae may play important roles in coral bleaching (van der 

  Zande etal. , 2020). Along the Indian coast, in the coral 

  reefs of Palk Bay( Bay of Bengal), varied bleaching and 

  recovery patterns among coral genera was observed 

  during the 2016 bleaching episode (Thinesh etal. , 2019). 

 Acropora species had the highest levels of bleaching 

  (86.36), followed by Porites (65.45), while Favites 

  Symphyllia, Favia, Platygyra, and Goniastrea showed only 

  mild to no bleaching. 

 cutting carbon emissions (bruno and valdivia,2016)limiting 

  warming to below 1. 5C is essential to preserving coral 

  reefs worldwide and protecting millions of people (Frieler 

  etal. , 2013 Hoegh-Guldberg etal. , 2017). 

 Many visitors to coral reefs have high environmental 

  awareness, and reef visitation can both help to fund and 

  encourage coral reef conservation (Spalding etal. , 2017). 

 About 42 percent of the mangroves on earth are found in 

  Asia, where the greatest mangrove forests are found. This 

  contains the Sundarbans, the biggest continuous 

  mangrove forest still existing in the world (Dashupta et al., 

  2020). 

 The biodiversity of mangrove environments is extensive. 

  Flora and a wide variety of living organisms, including as 

  mammals, birds, fish, crabs, shrimp, insects, and bacteria, 

  support and maintain the ecosystems. Mangrove 

  deforestation rates today are lower than they were in the 

  late 20th century. 

 Jones and Gandhi,( 2019),( 2019 Friess) et al However, the 

  trend continues in several parts of Asia. Asia's main 

  mangrove-loss hotspot is Myanmar, which saw 35 losses 

  between 1975 and 2005 and 28 losses between( 2000 and 

  2014). From( 2000 to 2012), loss rates in Myanmar were 

  four times higher than the global average. 

   

  key drivers to vulnerability 

   

 Studies by Sajjad et al. (2018) that evaluated the 

  vulnerabilities of coastal communities along the Chinese 

  coast have shown that approximately 25 of the coastline 

  and more than 5 million residents are in highly vulnerable 

  coastal areas of mainland China, and these numbers are 

  expected to double by 2100. Husnayaen et al2018 .'s 

  assessment of the Indonesian city of Semarang's coast 

  revealed that 20 of its 48.7 km of coastline is extremely 

  vulnerable. 

         

  observed impacts 

 Primary production in the western Indian Ocean showed a 

  reduction by 20 during the past six decades, attributed to 

  rapid warming and ocean stratification which restricted 

  nutrient mixing( Roxy etal. , 2016). 

 Variation in secondary-production zooplankton densities 

  and biomass in the East Asian Marginal Seas affected the 

  recruitment of fishes due to mismatch in spawning period 

  and larval-feed availability during the last three climate 

  regime shifts (CRS) in the mid-1970s, late 1980s and late 

  1990s, which were characterised by the North Pacific index 

  and the Pacific Decadal Oscillation index (Kun Jung et al 

  2017). 

 imulation experiments have shown differential adaptation 

  capacity of common species Zheng, 2019 Yuan etal. , 2019. 

  The UNs 2019 report on climate action and support trends 

  highlights that the impacts of climate change on coastal 

  ecosystems are mainly increased risks due to flooding, 

  inundation due to extreme events, coastal erosions, 

  ecosystem processes and, in the case of fisheries, 

  variations in population or stock structures due to ocean 

  circulation pattern, habitat loss degradation and ocean 

  acidification. 

   

  projected impacts 

   

 It has been established that the combined effects of water 

  pollution and climate stressors would be more detrimental 

  to ecosystem sustainability than any stressor acting alone 

  (Buchanan et al., 2019). 

 Climate conditions were shown to raise the pollutant stress 

  on seagrass meadows by 2.6% (from 39.7 to 42.3%). 

  Different scenarios, including RCP2.6 and RCP8.5, were 

  developed for the Bohai Sea, with the results indicating an 

  amplified impact on the ecosystem under the assumption 

  that the pollution levels stay at the levels of 2014. 

 The main pollution stressors were pollutants such 

  petroleum hydrocarbons, dissolved inorganic nitrogen, and 

  soluble reactive phosphorus (Lu et al., 2018). 

 Projected changes in catch potential in percent by 2050 

  and 2100 relative to 2000 under RCP2. 6 and RCP8. 5, 

  based on outputs from the dynamic bioclimate envelop 

  model and the dynamic size-based food-web models, 

  indicate that the marine and coastal resources of most 

  Asian countries will be impacted with varying intensity 

  FAO, 2018. 

 

  Table 

   

 Apart from these threats, natural hazards have also been 

  found to affect coral reefs of Asia. The extensive and 

  diverse coral reefs of Muscat, Oman, in the northeast 

  Arabian Peninsula were found to have long-term effects 

  from Cyclone Gonu, which struck the Oman coast in June 

  2007, more than coastal development( Coles etal. , 2015). 

  Sandy beaches are subject to highly dynamic hydrological 

  and geomorphological processes, giving them more 

  natural adaptive capacity to climate hazards (Bindoff et al 

2019).