REGUA created its wetlands in 2005 and 2007, with the generous funding by Mr Stephen Rumsey of the Wetlands Trust, UK and Dr Nancy Weiss from the US. Fed by a small water catchment of 100ha, the stream in the center of an area of cattle pasture was blocked to create a flooded area of 8 ha. A concrete lined outlet was constructed to ensure flooding would not erode its outflow.
When any area is flooded with fresh water, colonization by fauna and flora rapidly occurs fuelled by the suns energy and a new ecosystem is formed. Fortunately for the REGUA project, fresh water ecologist Professor Tim Moulton of the RJ state University (UERJ) visited REGUA with his wife orchid specialist Rosario at this moment of flooding and Tim saw the opportunity of monitoring a newly formed ecosystem to quantify these natural processes that make wetlands such a productive habitat.
Dissolved minerals and released carbon dioxide from remnant flooded vegetation give life to the smallest microscopic plant forms, phytoplankton. Phytoplankton is able to make organic compounds, the basis of the aquatic food chain and is known as agents for primary production. Feeding on phytoplankton is zooplankton, a category of organisms ranging from protozoans and metazoans, capable of independent movement and in turn also a food source. Healthy wetlands have an abundance of phytoplankton and zooplankton, both providing rich feeding fields for higher trophic levels, increasing the biodiversity associated with this habitat.
Wetland’s associated plants are called macrophytes and divided in three major categories; reeds, submerged plants and floating plants. They grow independently and are important for the biology of other water life. The depth of water is important and low levels of sunlight restrict the growth of reeds and submerged plants, but shallow water provide ideal conditions for submerged macrophytes. The surface can also be quickly colonized by floating plant species such as the common Wolfia, Azolla and Lemna but their build up reduces sunlight to the submerged plants. One submerged species is Egeria (common oxygen weed used in fish tanks) and it offers many higher order species a vertical structure for biodiversity associated with wetlands.
Generally associated with inundated low lying land, wetlands receive inflow from the surrounding land mass. As higher trophic order species invade this productive habitat a change of nutrient levels may be expected. Inputs such as sewage, land fertilizers, cattle manure or excessive bird roosting can push up the phytoplankton population and when this happens, the wetland becomes eutrophic. Water clarity or turbidity can be measured and excess phytoplankton may consume valuable oxygen leading to fish mortality in some cases in effect affecting the very health of the wetland itself.
We are very fortunate to have Tim’s son Lucas working on various experiments and his interest is testing the tipping point of nutrient build up, to discover at what stage does a wetland become eutrophic. He will be evaluating the quality of the submerged Egeria plants to tell him what value of point of Nitrogen (N) and Phosphorus (P), the two main elements causing eutrophic, is a wetland considered unproductive. He has designed some plastic tanks (mesocosms) which are used to isolate a portion of the water body and he is able to add varying doses of nutrients (NP) and gain an idea of the response of the aquatic ecosystem. So far he has been amazed to see that the plants are resisting extremely high doses and his studies are taking him to examine closely the reasons for their tolerance.
Aside the strategic importance of fresh water on this planet, wetlands are very important and productive habitats for our fauna and flora. They are increasingly used for stocking clean water and for cleaning domestic and industrial used water. The study of water habitats and their health as measured by aquatic macrophytes as a response to human related factors that generate nutrient fluctuations is of major importance to us all in relation to our future.