Implications of Acid Rain on Marine Ecosystems

A marine ecosystem is an ecosystem defined by an aquatic environment with higher salinity compared to freshwater ecosystems. These ecosystems are teeming with flora and fauna, providing one of earth’s major food sources. Covering over 70% of the Earth’s surface, marine ecosystems are divided into several broader types of ecosystem, such as estuaries, salt marshes, mangrove forests, coral reefs and open ocean. Marine ecosystems are characterised by a variety of unique biotic and abiotic factors. Important abiotic (non-living) features consist of sunlight, salinity, acidity, atmosphere, distribution of dissolved properties in the water, proximity to land, current, topography, depth, and temperature. Key biotic factors (living) include plants, protista, fungi, animals and microbes. Marine ecosystems are extremely diverse and differ based on climate, longitude and latitude.

Acid rain is any form of precipitation that is abnormally acidic (PH>7, a substance with a chemical property of elevated hydrogen ion levels). Acid rain can have adverse effects on ecosystems due to its corrosive properties. The amount of acidity in the atmosphere depends on the annual rainfall. There are two types of acid rain, dry deposition and wet deposition. Dry deposition is acidic gases and particle deposits from the atmosphere lacking any moisture. While wet deposition occurs when acidic substances such as sulfuric and nitric acids from the atmosphere fall to the earth’s surface in the form of precipitation, with the presence of moisture (rain, snow, sleet, hail) The acidic substances can accumulate on surfaces like infrastructure, buildings, vegetation (etc.) and potentially soak into grounds and water bodies. Acid rain is caused by a chemical reaction that occurs when compounds like nitrogen oxide and sulfur oxide rise into the upper atmosphere and react and combine with gases and other substances like water and oxygen, creating acidic pollutants. Most of these acids originate from volcanic eruptions, air pollution from factories, cars, etc. Some rain is naturally acidic, however human activities have worsened it.

Acid rain often imposes negative consequences on ecosystems flora and fauna. These effects are worsened in marine ecosystems due to the amount of evaporation. The impacts in streams and salt marshes are evident as it flows through topsoil, it may leach aluminum and carry it into the subsoil and other streams and lakes. Increased aluminium exposure can have neurodegenerative effects on animals, causing defects and population decreases in certain species who inhabit the water or consume it. With increased phytotoxicity in the soil caused by aluminum, root development ceases. Since H2O is brought to the plant via roots and xylem vessels to complete photosynthesis, energy production drastically decreases, causing it to die. Additionally, in the absence of roots and minerals, topsoil has a higher chance of being swept away by currents and extreme weather conditions, lessening the chance of new plant growth and removing primary consumers’ energy sources.

To summarize, organisms need the right PH to function and grow at their optimal rate, but if the PH is too low, it can have devastating effects on biotic factors of an ecosystem. Once acidic rain deposits into a body of water (e.g. ocean, salt lake, etc.) acid-sensitive organisms will suffer. The population of fish will decrease because most species of fish eggs aren’t able to grow and hatch in a PH of 5 and below. The other organisms that may be able to tolerate the acid could lose a major predator or prey, knocking the dynamic equilibrium out of balance, damaging biodiversity and the food web. Plus, ocean acidification causes a reduction in the distribution of carbonate, a key component of seawater. This puts marine organisms at a profound disadvantage, making it difficult for organisms like coral to form skeletons and shells. Coral reefs are vital to marine ecosystems for a myriad of reasons, If coral reefs were to be extensively damaged, marine ecosystems will suffer. Coral reef degradation could cause coastlines to be more prone to erosion, habitats to be destroyed, gas cycling to decrease, construction materials and food to decrease, etc.