1998 Year of the Ocean Ocean Living Resources 



and dams or other construction far upstream can alter habitats for anadromous species (those that 

 spend part of their life at sea, and part in fresh water) and alter sedimentation and water flow 

 downstream. 



Invasions of Exotic Species 



A marine scientist noted several years ago that the bottom of San Francisco Bay looked 

 much like the bottom of Tokyo Harbor. Species that were at home on the opposite side of the 

 Pacific had moved in and taken over, in some cases pushing out the local fauna. Over 234 exotic 

 species have been identified in San Francisco Bay and Delta, and exotic species may account up 

 to 99% of the biomass in some habitats (Cohen and Carlton 1998). The phenomenon, knovm as 

 invasions of alien or exotic species, is one of the least known threats to marine biodiversity. Non- 

 indigenous species are introduced both inadvertently and intentionally. Not all intentional 

 introductions are harmful. In the marine environment, for example, introductions of oysters and 

 other shellfish have been the basis of a multi-million dollar aquaculture industry. Yet, these same 

 introductions have also unintentionally introduced new disease organisms traveling in shipments 

 of the aquaculture species. 



Many introductions of marine organisms occur via the exchange of ballast water in 

 international shipping. The increase in international trade has greatly increased this pathway for 

 non-indigenous species introductions. Inadvertent introductions through ballast water have been 

 implicated in outbreaks of red-tide dinoflagellates in Australia; the invasion of the Black Sea by 

 the American comb jellyfish with disastrous effects on plankton biomass and the anchovy 

 fishery; and the invasion of the Great Lakes by Eurasian zebra and quagga mussels that have 

 caused great economic damage in inland waterways. In most cases, the ecosystem effects of 

 invasions of exotic species are still unknown. 



Global Climate Change 



Historically, changes in global climate have significantly altered the ecosystems and 

 processes of the world's ocean. Today, these natural changes are being joined by alterations to 

 the earth's atmosphere as a result of human activities. Chief among these are decreases in 

 stratospheric ozone caused by ozone-depleting substances such as chlorofluorocarbons, and 

 global warming caused by increased atmospheric concentrations of so-called greenhouse gases 

 such as carbon dioxide and methane, which are produced by human activities. 



Ozone depletion — particularly in higher latitudes — has resulted in increases of 

 ultraviolet-B (UV-B) radiation reaching the earth. A number of studies have confirmed that 

 increased UV-B can damage phytoplankton and zooplankton, the basis for much of the ocean's 

 enormous productivity. The world community has taken the issue of ozone depletion seriously, 

 and the Montreal Protocol to the Vienna Convention has set countries on a course to the phase- 

 out of most classes of ozone-depleting substances. 



C-21 



