Program

A coastwide toxic bloom of Pseudo-nitzschia in 2015 resulted in the largest recorded outbreak of the neurotoxin, domoic acid, along the North American west coast. Lengthy closures of razor clam, rock crab, and Dungeness crab fisheries resulted in economic and social damage to coastal communities. Domoic acid was measured in numerous stranded marine mammals, including dolphins, porpoises, harbor seals, whales, fur seals and a record number of sea lions. This outbreak was initiated by anomalously warm ocean conditions accompanied by the appearance of Pseudo-nitzschia australis north of its typical range in the nutrient-poor water spanning the northeast Pacific in early 2015. Laboratory and field experiments confirmed maximum growth rates of P. australis at elevated temperatures and enhanced toxin production with nutrient enrichment. These data, together with a retrospective analysis of less widespread toxic events, demonstrate the potential for devastating ecological and economic disruptions in the rapidly changing climate.

Dinophysis rotundata, a toxic dinoflagellate, has been known as an active predator feeding on planktonic ciliates. However, little information is available on the prey species and diversity because D. rotundata has not been successfully cultured so far. We tried to identify its prey organisms by analyzing the intracellular genes of D. rotundata. Four cells of D. rotundata were isolated from the natural sea water collected from Ise Bay, Mie Prefecture, Japan from 2013 to 2016. The isolated cells contained clear food vacuoles, indicating prey cells preserved well in the vacuoles. After washing each cell and putting into a PCR tube, DNA extraction was done. PCR amplification was conducted using a universal primer set. A restriction enzyme which cleaves selectively only D. rotundata DNA was treated to concentrate the prey DNA. More than 200 sequences were analyzed using gene cloning. DNAs of planktonic ciliates such as tintinnid species (Tintinnopsis radix and Helicostomella subulata) and aloricate ciliate species (Strombidinopsis acuminata) were detected from the prey DNA. Moreover, DNAs of radiolarians, bivalves, polychaetes, and rotifers were also included in the prey DNA. These results harvested by this molecular analysis imply that the food history of prey organisms inside D. rotundata can be tracked. Further application of this technique can provide useful data to revise the structure of food webs in planktonic ecosystem.

It is empirically known that HABs by noxious flagellates such as Chattonella and Karenia have occurred when diatoms are scarce in water columns. Diatoms produce resting stage cells under nutrient-depleted conditions, and rapidly sink to sea bottom and disappear from the water columns. Giving enough light to the abundant diatom resting stage cells is considered to enhance their germination and resultant vegetative cells are expected to rapidly proliferate in the surface water and to overwhelm harmful flagellate populations by the exhaustion of inorganic nutrients (N and P). Simulating these situations, we made bottle experiments containing small amounts of bottom sediments and noxious flagellates of C. antiqua and K. mikimotoi in Saiki Bay of Oita Prefecture, Japan in 2014. Sediments containing diatom resting stage cells stored in a refrigerator were added into 2L volume transparent pet bottle at concentrations of 0.1g L^-1 and 0.01g L^-1. K. mikimotoi was inoculated at a concentration of 20 cells mL^-1 and C. antiqua 50 cells mL^-1. The 1/100 strength of SWM3 medium was added as nutrient source for phytoplankton in the bottles. These bottles were hanged at surface and the depth of 5m, and samplings were made for cell enumeration of flagellates and diatoms, and for nutrient measurements. Diatoms grew well in all the bottles examined, though faster growths were observed in the bottles at 0m. C. antiqua was easily overwhelmed by proliferated diatoms after the incubation period. K. mikimotoi slightly increased to 70 cells mL^-1 at most, and then decreased. It is suggested that sediment-lift is a possible strategy to prevent harmful flagellate red tides. The most abundantly appeared diatoms were belonging to the genus Skeletonema.

It is known that the noxious red tide dinoflagellate Karenia mikimotoi has caused mass mortalities of aquaculture fish in western Japan and northern distribution has been limited to Tokyo Bay and Maizuru Bay in Japan. In this study we first detected the K. mikimotoi cells and bloom occurrence in 2015 in Hakodate Bay, Hokkaido, Japan. The dynamics of K. mikimotoi were investigated in Hakodate Bay in 2015 and 2016. Samplings were conducted 1 – 4 times in every month at the point at the wharf of Hakodate Research Center for Fisheries and Oceans (Stn. HKK). K. mikimotoi cells of 2 cells mL^–1 (0 m) and 1 cell mL^–1 (5 m) were first detected on 31 August 2015, and cell densities increased to form a red tide in November. Water temperatures were 10.2 – 15.6˚C during this period. In 2016, the first detections of K. mikimotoi was 4 cells mL^–1 (0 m) and 12 cells mL^–1 (5 m) at Stn. HKK on 27 September, and the maximum density reached 34 cells mL^–1 (5 m) on 27 October, thus stayed small bloom. The cell densities of diatoms were low (<10³ cells mL^–1) in October and November in 2015 and 2016, since the global solar radiation declined (≒5–10 MJ m^–2) during October and November in Hakodate area. In 2016, the water temperature rapidly declined from the late October to early November by the effects of a strong cold snap that hit Hokkaido in late October. Adverse environmental conditions probably inhibited the growth of K. mikimotoi in 2016. Appearances of K. mikimotoi both in 2015 and 2016 suggested that K. mikimotoi cells were transferred as a natural dispersal by the Tsushima/Tsugaru warm currents or via ships’ ballast water.

The landings of coastal fisheries have been declining since the 1980s in Japan. Environmental deterioration is often cited as a major factor for the declining. Coastal areas are interacted with lands as they are profoundly affected by freshwater through rivers and groundwater. The land use structure composed of forests, farming grounds, rivers and cities that stimulate human activities have large impacts on the coastal environments and ecosystems. This should be inherently linked to the deterioration of biological production in coastal areas. This concept has been widely spread in the last decades, and recently fishermen have been planting trees in the catchment areas to improve water quality in their fishing grounds.
Three important points should deserve considering as the effect of land use structure on coastal ecosystems. Firstly, it has long been believed that nutrients from forests fertilize sea water. It is revealed by the fact that biological production in the coastal area is considerably higher than that in open ocean. However, the detailed mechanisms of nutrient supply from forests to rivers and groundwater remain unknown. Some recent studies have emphasized the importance of wetlands and paddy fields as sources of nutrients. Secondly, forests stabilize water discharge, as they conserve surplus water supplied by heavy rains. This effect is especially important in Japan that has large precipitation and precipitous mountains. Thirdly, the components of particles supplied to coastal areas are largely attributable to the land use. A certain amount of sand should be supplied to maintain sandy beach. However, inflow of abundant mud has negative effects on benthic organisms as it inhibits normal aspiration and hinders photosynthesis.
In contrast to the upsurge of the social activities, scientific demonstration that shows clear positive effects of forest on the water quality is inadequately conducted. Further studies on the land-sea interaction is desperately required.

Indonesia is the largest archipelago in the world. Its coastline is about 95.181 km with a sea area of 5.4 million km². Indonesia has 1.2 million hectares (ha) of brackish water pond area, but only 37.5% of them are used for aquaculture activities. While, marine culture area is only used about 2% from 4.5 million ha that is available. The low utilization of brackish water pond and marine culture area are generally caused by environmental damage due to the excessive exploitation by intensive aquaculture activities during the period of 1980s and the limitation of seed, capital and technology. In line with the growing global paradigm in the face of change and good environmental damage caused by excessive exploitation of natural resources and the consequences of climate change and global warming, it is time for Indonesia to implement the concept of management and utilization of natural resources taking into account the balance and stability of the natural resources and the environment, such as in the concept of SATO-UMI. The Integrated Multi Tropic Aquaculture (IMTA) on the bases of bio-recycle system and Sato Umi concept should be applied for sustainable aquaculture. An experiment of the IMTA in the brackish water pond as a close system method (CSIMTA) has shown a good performance on the production of multi species fisheries commodities as well as water quality stability. On the onshore area, developing of open system method of IMTA (OSIMTA) by combining seaweed culture and floating cage of multi species fisheries commodities seem also has a good prospective to improve productivity of coastal area. In the future, developing aquaculture models using the biorecycle system to reduce and minimize the inorganic and organic waste from the remaining feed, faeces and the other sources will be useful to maintain sustainable aquaculture in the coastal area.