Benthic fauna of the inner part of ariake
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This document summarizes a study on changes in benthic fauna in the inner part of Ariake Bay between 1989 and 2006. The mean number of species, abundances, and biomass of macrobenthos declined significantly over this period. Benthic communities shifted from large, long-lived species to smaller, short-lived species, indicating long-term organic pollution. Distribution of dominant bivalve species also changed. The deterioration of the benthic ecosystem is likely due to increased hypoxia, sediment changes, and pollution stressors in the bay. Continued monitoring is needed to inform management decisions for restoring marine ecosystems and benthic habitats in Ariake Bay.
Benthic fauna of the inner part of ariake
- 1. Benthic fauna of the inner part ofBenthic fauna of the inner part of Ariake Bay: long-term changes inAriake Bay: long-term changes in several ecological parametersseveral ecological parameters Presented by : Fiddy Semba Prasetiya Vrije University of Brussels of Marine Biodiversity Partim Benthosf Marine Biodiversity Partim Benthos, Vrije University of Brussels, November 20, Vrije University of Brussels, November 20thth 20082008
- 2. General IntroductionGeneral Introduction • Role of benthic ecosystems in marine ecosystems Nutrients Phytoplankton Zooplankton Fish Detritus Sediment Resuspended sediment Benthic Organisms Bacteria
- 3. Purification process Sediment Organic loads Toxic substances Organic loads Toxic substances Water column
- 4. Environmental change inEnvironmental change in Ariake BayAriake Bay Reclamation dike in Isahaya Bay • Decrease in particle size of sediment • Increase in transparency • Decrease in tidal amplitude Disturbance on benthic ecosystem: • The increase in red tides and hypoxia • Decreasing of bivalves catch
- 5. Atrina spp. Scapharca spp Ruditapes philippinarum Source: www.naris.go ; www.hk-fish.net
- 6. Objective of ResearchObjective of Research • To investigate the subtidal benthic fauna of the inner part of Ariake Bay, • Compared statistically the changes in the benthic fauna between the present data and the 1989 data in Koga (1991) which indicates the condition before the ecosystem degradation
- 7. Study siteStudy site • This research is located in the inner north part of the bay • The inner part of Ariake Bay mainly consists of vast tidal flats and shallow subtidal area of generally less than 15 m in depth, and is roughly divided into two parts according to bottom type: - The muddy western part off Rokkaku River and Shiota River estuaries with 6 to 7Mdφ - The sandy eastern part off Chikugo river 34Mdφ • This research is located in the same stations as Kasagi et al. (2007); 45 subtidal stations with 28 mud and 17 sand bottoms
- 8. Study Site Source : www.unepatlas.com
- 9. Location of the study site and the sampling stations Note: - Dashed lines indicate contour depth (m) - Dotted points are mud bottoms, and - The squares are sand bottoms
- 10. Sampling and processingSampling and processing • Sediment sample was taken by using a Smith-McIntyre grab sampler (22.5 x 22.5 cm), and gently sieved the sediment with a 1 mm opening mesh • The residual samples on the mesh were fixed with 10% formalin solution stained with Rose Bengal, and brought to the laboratory. • The animals were sorted out, identified to the lowest feasible taxon, and counted • The bulk wet weight was weighed for each species by pooling individuals using an electric balance nearest to 0.001 g
- 11. Estimation of species richness This estimate is based on the observed frequency of rare species in the community and obtained from: Where: s = observed total number of species n = total stations k = number of unique species Fj= number of stations containing unique species
- 12. Results and discussionResults and discussion Benthic fauna in muddy and sandy bottom:Benthic fauna in muddy and sandy bottom: - 51 Polychaeta species51 Polychaeta species - 25 crustaceans25 crustaceans - 23 molluscs23 molluscs - A few brittle stars and a sea cucumberA few brittle stars and a sea cucumber - 2 stations in the muddy area had no organism2 stations in the muddy area had no organism The mean number of species per station was significantlyThe mean number of species per station was significantly higher in the sandy bottom than in the muddy bottomhigher in the sandy bottom than in the muddy bottom (mean(mean±SE; mud = 5.5±0.8, sand = 15.2±2.3)±SE; mud = 5.5±0.8, sand = 15.2±2.3)
- 13. The mean abundances of each taxon in 1989 and 2006 Total macrobenthos, polychaetes,ophiuroidea and others in 2006 were significantly fewer than those in 1989 The decrease in bivalves was nearly significant, and that in crustaceans did not differ between the two years
- 14. The relative abundances of each taxon in 1989 and 2006 No interactions between taxa, bottom type and years Compositional patterns of taxa were similar irrespective of bottom types and years
- 15. The relative biomass of each taxon in 1989 and 2006 There was no significant difference in the biomass of any taxa between the two bottoms, except that Ophiuroidea tended to be lower in mud than sand The relative biomass of each taxon did not differ between the bottom types In the sandy bottom, total biomass in 2006 was 96.851.0 gww/m2 , about 45% of which was bivalves on average
- 16. The Distribution of dominant bivalve species
- 17. The Distribution of dominant bivalve species
- 18. The Distribution of dominant bivalve species
- 19. The Distribution of dominant bivalve species
- 20. The Distribution of dominant bivalve species
- 21. The Distribution of dominant bivalve species
- 22. Suspected causes for decrease inSuspected causes for decrease in the macrobenthosthe macrobenthos • The occurrence of bottom hypoxia in summer • The change in sediment grain size • Benthic succession from large long-lived to small short lived species assemblages with long- term organic pollution on the bottom Dominating species of Theora fragilis, Raeta pulchellus, Paraprinospio and capitellidae pollychaetes
- 23. Benthic indicators of organicallyBenthic indicators of organically polluted areapolluted area • Source: www.microseashell.com Theora fragilis Raeta pulchellus Capitellidae polychaetes
- 24. ConclusionsConclusions The benthic ecosystem of the inner part ofThe benthic ecosystem of the inner part of Ariake Bay has clearly deterioratedAriake Bay has clearly deteriorated There is a changes in benthic ecosystems fromThere is a changes in benthic ecosystems from the decline in abundance, biomass and thethe decline in abundance, biomass and the distribution of dominant species between 1989distribution of dominant species between 1989 and 2006and 2006 Recovery of benthic ecosystems in the inner partRecovery of benthic ecosystems in the inner part would be unlikely unless those stressors arewould be unlikely unless those stressors are removedremoved
- 25. Benthos research in relation with marineBenthos research in relation with marine ecosystem managementecosystem management Monitoring habitats and ecosystems is desirable to detect the changes happening within the reserve and provide conservation managers with information to base management decisions on Monitoring is recommended for every years
- 26. Terima Kasih Thank you Dank u Merci Gracias Arigato gozaimas
- 27. Distribution of capitellid and spionidDistribution of capitellid and spionid polychaetes in 2006polychaetes in 2006
- 28. Distribution of gammaridea in 1989 and 2006Distribution of gammaridea in 1989 and 2006 YearYear Occurring frequency ofOccurring frequency of mud (%)mud (%) Occurring frequency of sandOccurring frequency of sand bottoms (%)bottoms (%) 19891989 81.881.8 33.333.3 20062006 50.050.0 76.576.5