Post #258702 by TikiJosh on Tue, Oct 3, 2006 12:59 PM

The answer to the question about why California has more plankton, etc. than a tropical place like Hawaii relates to the ocean currents in those areas. Tropical regions, such as Hawaii, generally have very nutrient poor water. The corals are experts at nutrient recycling which is why they can live in relatively clear, clean water, and probably also part of the reason why they grow so slowly. The coral polyp produces waste just like any animal, and the symbiotic algae use that waste for photosynthesis. Because there's not a lot of nutrients floating around, you don't get dense areas of seaweed/kelp/algae/phytoplankton, at least not like the kelp forests of California.
The reason California is so special is because our main current is the California current, which comes from the north and heads south. A current moving from north to south produces Ekman transport to the west. I'm sure there's tons of info on Ekman transport online if you want to read more about it, but the gist is that as surface water moves, it can "drag" some of the water under it, but it doesn't drag in a perfectly straight line. The lower layers tend to almost spiral, until you get some water moving perpendicular to the original direction of water flow. In other words, a current moving to the south can cause lower layers of water to move to the west. Generally, as water moves by Ekman transport, the surrounding ocean fills it in. In California, however, there's just a lot of land to the east, so deep water fills in the gap left by Ekman transport. This process, called upwelling, brings nutrient rich water from very deep in the ocean which can feed phytoplankton blooms and kelp forests.
And that's why the ocean is greenish in California and nice azure blue in Hawaii.