Yes algae is growing because there is a more than enough CO2 in the warming ocean water. This is why ocean acidification is taking place and killing the coral. It is also why toxic Cyano-bacteria (Blue-green algae) is becoming more prevalent and causing health issues.
The only fish populations that are increasing are the smaller species like sardines and herring. This has occurred solely due to overfishing of the predator species. No direct connection to global warming/climate change.
Yes you are right but again everything does something in nature. Algae takes in CO2 and gives back Oxygen. Start tinkering with algae and you can start something that can't be stopped. My whole point is that until scientists are 100% sure that there is a problem a REAL problem like an asteroid headed for the earth that they shouldn't be fooling with the very make up of the earth. There is enough controversy surrounding the climate. When something can't be answered the response is always that climate change is causing it. If the numbers aren't showing that the earth is warming as predicted then just beat the numbers until the confess. The numbers will always confess for either the skeptics or the other side.
Benefits of Algal Blooms
Algal blooms provide large concentrations of algae that produce organic compounds needed by higher organisms, ranging from oysters, clams, and mussels to human beings. For this reason, productivity increases in areas where algal blooms occur. More algae in the water means that more carbon dioxide is used from the atmosphere and that more oxygen is released into the atmosphere. Oxygen is necessary for many living things, including humans. As noted previously, the production of dimethyl sulfide gas helps protect algae from harmful ultraviolet rays so they remain healthy and thus are able to continue the cycle of sustaining life on Earth.
Even in the coldest parts of the ocean, algae provide the primary source of organic material to animals at the bottom of the food chain. Organic materials are moved up the food chain as higher organisms feed on those lower down the chain. For example, algae have been found in Antarctic sea ice. As sea water freezes, algae living in the water are frozen in the ice, where they later can be released during a thaw. These algae are a vital source of food for krill, the shrimp-like organisms eaten by penguins, seals, seabirds, and whales.
Read more:
http://www.waterencyclopedia.com/A-Bi/Algal-Blooms-in-the-Ocean.html#ixzz4RVFkmbCQ