Ocean Acidification Threatens Marine Ecosystems and Livelihood Security in Bangladesh M. Shahadat Hossain, S. M. Sharifuzzaman, Sayedur R Chowdhury, Subrata Sarker and Shah Nawaz Chowdhury Institute of Marine Sciences and Fisheries, University of Chittagong, Bangladesh
Rising atmospheric carbon dioxide (CO 2 ) leads to lower oceanic ph and increase sea surface temperature (SST) Fossil Fuels, Coal, Oil, and Gas and Volcanic Eruptions Atmospheric CO 2 Mixing CO 2 (aqua) H 2 O H 2 CO 3 H + + HCO 3-2H + + CO 3 2- ph = -log [H + ] When CO 2 dissolves in seawater it forms carbonic acid (H 2 CO 3 ), which dissociates to form equilibrium with hydrogen ions (H + ), bicarbonate ions (HCO 3- ) and carbonate (CO 2-3 ). This equilibrium is dominated by bicarbonate, (CO 2 1%, CO3 2-8% and HCO - 3 91%, of total dissolved inorganic carbon Source: Havenhand 2012
Have there been recent changes in ocean acidification? Ask the coral of the Bay of Bengal
Historical trends: ph and SST SST showed increasing trend, whereas water ph has decreasing trend in the northern Bay of Bengal, Bangladesh Data source: Islam (2000), Kamrul (2005), Chowdhury et al (2009), Samsuzzaman (2009), Mamun (2010), Nai et al (2011) and Hossain et al (2012)
An average ph of 7.8, 7.6 and 7.3 in the years of 1970-1979, 1980-1989 and 1990-1999, respectively, clearly indicates a declining trend Data source: National Oceanographic Data Center (NODC) (http://www.nodc.noaa.gov/oc5/ WOA09/) Hossain et al. 2013
Moreover, an average SST of 28.39⁰C, 28.86⁰C, 29.31⁰C and 29.39⁰C during the years 1970-1979, 1980-1989, 1990-1999 and 2000-2010, respectively, shows a rising trend Hossain et al. 2013
Lower oceanic ph and increase SST are unfavourable for the growth, survival and reproduction of marine calcifiers such as coral reefs, molluscs and other shelly organisms Coral reefs of Northern Bay of Bengal, Bangladesh (2014)
The records of coral species in the northern Bay of Bengal, Bangladesh Year Coral species Temperature (⁰C) ph Reference 1997 66 28-29 - Tomasik, 1997 2008 40 27.5-29.5 7.5-7.8 Sultana et al., 2008 Among the 66 coral species in 1997, only 40 species were recorded in 2008, which indicates 26 coral species lost in 11 years, posing serious threat to the coral biodiversity in the northern Bay of Bengal Bangladesh Lowering the oceans ph levels results coral bleaching, slow growth and decrease coral species diversity Northern Bay of Bengal, Bangladesh
Oysters, mussels, barnacles from the Moheshkhali Island, Bangladesh (2013)
Increased ph (2004-2012) reduced oyster spat settlement and growth in the northern Bay of Bengal
Effects on marine capture fisheries: 1986-2010 Catch per unit effort (CPUE) reduced in the northern Bay of Bengal during 1986-2010, which indicates declining trend for the net CPUE and lower production of marine capture fisheries in the northern Bay of Bengal Negative value shows a decline in CPUE from the previous year and positive value indicate increase in CPUE from the previous year
Fish species abundance in the GBM estuary Water ph was the most important hydrological factors followed by dissolved oxygen, transparency and water temperature on species distribution at the Ganges-Brahmaputra-Meghna River estuary, northern Bay of Bengal Hussain (1971) reported 475 finfish species from the coastal and marine waters of the Bay of Bengal Islam et al. (1993) reported 185 species of finfish and shellfish Chwdhury et al. (2011) recorded 98 finfish, 23 species of shrimps and prawns, 13 crabs, 11 species of molluscs, 3 echinoderms and 4 other crustaceans from the Naaf River Estuary Hossain et al. (2013) identified 53 finfish species from the Ganges- Brahmaputra-Meghna River estuary
Habitat shifting of reef-based organisms Spawning, feeding and nursery grounds of reef-based organisms may shift and thus affect species diversity, abundance and distribution Reef fisheries (fish, shrimp, crab, lobster), many of which are commercially important, may face probable extinction, if reefs disappear
Effects of ocean acidification on coastal ecosystems Mangrove Damage seedlings Slow mangrove regeneration Damage breathing roots Dying roots upwards Mangrove mortality Decrease biodiversity Molluscs Decrease fertilization Decrease embryo development Reduce calcification Shell dissolution Reduce metabolism Retired growth Increase mortality Plankton Alter physiology Reduce thermal tolerance Decrease aerobic scope Plankton bloom Increase mortality Retired growth composition Atmospheric CO 2 Dissolve CO 2 H 2 O H 2 CO 3 H + + HCO 3-2H + + CO 3 2- Coral reef Decrease productivity Break down symbiotic relationship Decrease calcification Mass bleaching Reduce growth Increase mortality Decrease aquatic biodiversity Fisheries Diminish olfactory and auditory ability Increase ventilation Reduce metabolic capacity Reduce energy conversion efficiency Low feed intake Decrease embryogenesis Increase mortality Decrease fisheries biodiversity Aggregated effects can, in the long run, modify the ecosystem functioning and services with significant implications on food security, nutrition, coastal livelihoods and multi-billion dollar fishing industry
Cause-effect analysis of ocean acidification Coastal livelihood in peril People become Homeless, income less, food less Damage natural barrier Coastal erosion Salinity intrusion Wave/current damper Decline Fisheries Finfish, Shrimp, Crab, Molluscs, Seaweeds Affect key ecosystems Cyclone and storm Severe & frequent Decrease fishing day Increase fishing cost Decline fish catch Coral reefs Molluscs bed Seaweed bed Seagrass bed Mangrove forest E F F E C T S Hamper oceanic food chain Organism s physiological disturbance Change organisms interactions Ocean acidification PROBLEM OCEAN Decrease water ph Organic matter breakdown Nutrients, algal bloom Temperature Salinity Dissolved oxygen Carbon sequestration in ocean water ATMOSPHERE Global warming C A U S E S Increase atmospheric CO 2 Fossil fuel combustion Industrial revolution
Past emissions of CO 2 in the atmosphere will continue the acidification process, even it is reduced substantially However, impacts of ocean acidification on marine fauna and ecosystem processes are poorly understood, and virtually limited science works have done in the northern Bay of Bengal, Bangladesh Therefore, adequate research and continuous monitoring programme is required to determine the current and future costs of ocean acidification in Bangladesh Development and implementation of specific action plans and adaptation strategies to deal with ocean acidification is a priority
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