Can somebody please explain the situation in Florida with all the fish and sea creatures dying in great numbers?

You have to understand the hydrology of Florida first. The Kissimmee River that drains the main watershed of north-central Florida flows into Lake Okeechobee. The Kissimmee watershed is a major agricultural area, producing much of this country's produce and citrus crop. Because of the heavy rains the fertilizer run-off from the farms along the Kissimmee causes algae blooms in the Lake Okeechobee, which then flow through the Caloosahatchee River into the Gulf of Mexico. The algae can be toxic, and as the marine life consumes the algae, the toxin enters the food chain: as the fish eat the organisms that eat the algae, the toxins accumulate in their bodies, then the predators who eat the fish also get a dose of toxins. Furthermore, as the marine life dies from the toxins, the decay of their bodies causes low dissolved oxygen levels in the water, leading a chain reaction of more marine life die off.

For some time a high pressure system over the Bahamas dominated the weather over Florida, The clockwise air circulation around that high pressure system caused the winds over Florida west coast to blow from the west and southwest, pinning the oxygen-poor water against the shore and washing dead fish on the beaches of Sarasota County. The high pressure system is now shifting to the north and the winds are shifting to the southeast pushing the red tide out to sea.

While the red tide can occur naturally, there is no doubt that over-fertilizing of the fields, combined with the destruction of the wetlands that can absorb the excess fertilizer run-off is a major contributor to the frequency and severity of red and blue tides.

Google the words 'red tide'.

It is called red tide, when some micro-organisms that produce toxins experience a population boom. A high concentration of these organisms turn the water red. The toxins kill animals that ingest the toxins or they eat prey that have a high level of toxins in their bodies They can also kill if the decaying process uses up all the oxygen that is dissolved in the water. Algae booms that do not contain toxins can do the same to fish, which extract oxygen from water. Too low a level of oxygen suffocates the fish. Dolphins and marine animals like sea turtles and manatees breathe oxygen directly from the air, but they can be killed if they ingest too much toxin.

Red Tide algae has toxins in it that the prey animals being consumed by the mammals have taken in, and thus the consumers get sick and die. Humans die that way as well, from eating shellfish that are contaminated by the toxin. Not all algal blooms involve toxic life forms, but when the blooms do involve such life, the food chain gets poisoned. So, the oxygen deprivation is not the only issue, although it is a major one. Also, water gets filled with some pretty nasty organisms when there is a large die-off even when there is no hazard from the algae itself, and those death-eating life forms can also be a source of illness. Some animals are way more tolerant of the nasty bacteria etc. that degrade dead flesh. Not all animals are like buzzards and have a high tolerance for that stuff.

Red Tide algae is also toxic, it isn't just oxygen depletion that makes it dangerous. The first reports of Red Tide were from the Spanish Conquistadores back in the 1400's. It isn't a new development.

The situation is you have a land mass called the Everglades which basically flows water across the whole state on the end and there's a lot of farms in there .. what happens is the runoff from all the chemicals they use on the farms goes into the sea water and drastically changes the ecology in the oceans surrounding the coastline ...