Primary Producers

Primary producers (plants and algae) are a necessary part of biogeochemical cycling.  Think photosynthesis – without the ability of plants to convert water and CO2 into food and oxygen, humans and other animals would be unable to eat and breath.  When plants take in carbon dioxide through photosynthesis, they break apart the CO2 molecule and use the carbon to grow (in other words, use it to create their “biomass“).  When we eat plant materials and products, we eat that carbon that they have fixed and eventually return it to the atmosphere through exhaling, or to the soils to be decomposed.

Increased levels of ultraviolet light, especially the shorter “UV-B” wavelengths, can cause damage to living tissue and changes in their makeup.  There are several types of changes that generally occur:

  1. Morphological changes, or changes to the actual plant structure and chemistry
  2. Phenological changes, or changes to the timing of life cycle events (for example blooming, losing leaves, etc.)
  3. Changes in DNA

The most significant morphological changes that have been observed are the reallocation of energy, usually from photosynthesizing to producing protective compounds (to shield them from excess UV-B). Also, they may devote more energy towards repairing cells and DNA damaged by the radiation. This can mean that plants themselves can change their chemical composition, which in turn will alter the nutrients they add to their ecosystem when they lose leaves or die.  Another significant effect this may have on ecosystems is that when they shift their allocation of resources to protection from UV-B and DNA repair it comes at a cost, often to reducing the amount of photosynthesis they do and thus the carbon they fix.

Research focused specifically on algae, another primary producer, has shown varying results with regards to whether their productivity will increase or decrease and how their biochemistry will change. One study showed that, although the amount of carbon fixed by algae decreased, biomass actually increased with additional allocation to protective compounds (Bothwell et al., 1994).

Any effect of ultraviolet radiation on plants, whether it leads to changes in chemical composition or changes in productivity (CO2 intake and incorporation into growth), is likely to have consequences for other organisms involved in a given system’s food web. As food webs are tightly linked and (for the most part) balanced in their natural state, a small fluctuation in one component or organism is likely to in turn affect other organisms they either consume or are consumed by, as well as those they share a similar niche with.

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