Increased carbon dioxide in the atmosphere leads to an increase in carbonic acid in the ocean, making oceans more acidic. Why is this a concern?

Most of our knowledge of the direct effects of ocean acidification on marine organisms
focuses on species known as “marine calcifiers” (e.g., corals, mollusks) that build
skeletons or shells made of calcium carbonate. Many of these species will suffer from an impaired ability to build skeletons as too much carbon dioxide produces carbonic acid, which corrodes shells. We know less about the direct impacts of acidification on harvested species like fishes and squids. In these species, the response to acidification is likely to involve physiological diseases including acidosis of tissue and body fluids leading to impaired metabolic function. Egg and larval stages are likely to be much more susceptible than adults, suggesting that reduced reproductive success will be among the first symptoms to appear.

Why is “ocean warming” a concern?

All species are adapted for life over a relatively moderate range of temperatures
compared with the extremes experienced from the poles to the tropics. Temperatures
below the optimal range slow the rate of metabolism and can become lethal if too low.
Temperatures above the optimal range increase metabolism and, because warmer water
contains less dissolved oxygen, a thermal threshold is reached where respiratory demand
exceeds the capacity for oxygen uptake. This is sometimes referred to as the “temperature oxygen squeeze.” Hence, temperature is one of the primary environmental factors that determine the geographic range of a species.

Fish are dependent on suitable water temperatures for their metabolism to survive. In recent years, warm–water species have increased in Long Island Sound, while cold–water species have declined

What is the impact to Long Island Sound?

Most of the cold-water species of Long Island Sound have been declining over the past 15 years (e.g., lobster, winter flounder, Atlantic herring, cunner, longhorn sculpin, sea raven, ocean pout, winter skate, and little skate), while most of the warm-water fishes have been increasing (e.g., striped bass, weakfish, summer flounder, menhaden, scup, striped sea robin, butterfish, Atlantic moonfish, hickory shad). Finally, there is also evidence from Long Island Sound that the recent trend of warmer winters favors the growth and recruitment of invasive species over those of native species. Researchers from the University of Connecticut showed that exotic ascidian species (sea squirts) benefit more from mild winters, while native species benefit more from cold winters.

 Lobsters are facing difficulties tolerating warmer temperatures
 

What preventive measures should be taken?

Resource managers need to recognize that local populations of species near the limits of
their distributional ranges will need additional precautionary measures to protect them
from extinction. Warming and acidification represent additional stresses that make
populations less resilient to the effects of harvest. We may need to reduce harvest of
some species in certain areas to enable them to withstand the additional stress.

The ultimate and best solution is the reduction of greenhouse gases that cause
acidification and warming.

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