In this video, we are going to talk about freshwater ecosystems. First of all, I would like to talk about the hydrosphere, which is all water on the Earth. This means oceans, lakes, ponds, rivers and also snow, ice and for example, the groundwater. So the water covers approximately 71 percent of the Earth. Probably, that's why sometimes and often the Earth is called the blue planet. From all this part that it's covered by water, 97 percent is covered by oceans, and the rest, the three percent is freshwater. So here in this table, you can see the percentages of the different types of freshwater ecosystems. If you take attention to the percentage of freshwater, different types of ecosystems, you will see that around 69 percent of the freshwater ecosystems are found in ice, glaciers, and permanent snows. So this is most of the water that we can find in this freshwater ecosystems on the Earth, the most part. Then we have about 30 percent of the water in the groundwater. Then we would find the rest like the water that we find in the lakes, rivers, and also for example in ponds, or other type of ecosystem. So we see how these ponds, lakes and rivers, in fact, they are most of the part of the freshwater ecosystems. They represent a little percentage on the Earth. Okay. Now, I would like to talk about the abiotic factors that influence the freshwater ecosystems. As in any other ecosystems, these abiotic factors have an important role. Concretely in these freshwater ecosystems, there are factors like the water temperature, the sunlight, the chemistry, the depth, the flow, and also the dissolved oxygen. These are some of the most important abiotic factors influencing these type of ecosystems. So here you have a diagram of a lake. In this lake, we see that there is a stratification. This is in fact, an example of lake that is stratified by temperature, and we have two parts. At the upper part, we find the epilimnion. This is the part of the lake that is influenced by the wind, so that there is a fluctuation or movement. Also, this is the part that can have an exchange of gases like oxygen or carbon dioxide, and also, this is the part that receives the most part of the sunlight. So that we find most of the phytoplanktons in this upper layer of the lakes. So that when phytoplankton reproduces and grows, and finally it dies, finally, it goes and falls into the epilimnion, which is the more cooler and lower part of these lakes. We have watched a sunset in the Mediterranean wetlands, and also we have heard amphibians calling. Concretely, we have heard for the toad, the Bufo calamita spring calling. These images come from a project that is called the amphibian observatory, and it is led by three coordinators. This is me, Maria Pefaree, and also Cecilia Needham. We try to study the distribution and conservation status of the different amphibians of the wetlands in Northeast of Catalonia. Also, we try to link these abundances and distributions to drivers of global change. Here, you can see some pictures of ourselves sampling at night, because amphibians are a nocturnal group of organisms, and they have these activity at night, and this is the best moment to sample them. So we do normally, visual and also auditory sensors. We measure some variables like water quality or habitat fragmentation, to have information of these global drivers. Another person I would like to introduce is Michelle Boone. She has done many research linking ecological and conservation science using amphibians. Because in fact, amphibians are a group of organisms that have part of their life cycle in the land, and the other part happens in the water. So that they can give us information of many aspects related to the different types of environments. Michelle Boone has done a lot of work using amphibians as biological indicators, and also studying the effects of pollutants, and pathogens, and also habitat fragmentation effects on amphibians populations. So many of the things we have been talking about are related to a part of science which is called limnology. Limnology is the study of the inland aquatic ecosystems. More concretely, the study of limnology includes biological, chemical, physical and geological characteristics of these ecosystems. We can find different types of freshwater ecosystems. We have talked about some of them like the ponds, the lakes or the rivers, and also there are springs or reservoirs, streams, and also the groundwater or wetlands. Now, I would like to present the main types of living organisms that we can find in this freshwater ecosystems, which are basically the fitoplancton, zooplankton, the macro-invertebrates, the macrophytes. Macrophytes are the plants that we find in the freshwater ecosystems, and also some vertebrates like amphibians or fishes. Now, I would like to introduce Margaret Ann Chapman. She studied basically macro-invertebrates and other types of invertebrates in freshwater ecosystems. She was the co-author of the Guide of the Crustacea of New Zealand. Also, her research is known because she was the first woman to lead a scientific expedition to the Antarctica. Concretely, she led an expedition to make a limnological survey of frozen lakes of the Taylor Valley. Another person that in fact, is not a limnologist, is an ictiologist, is Armonia Socorro Alonso. I would like to introduce her because she's a co-author of a reference textbook of the Freshwater Fishes of Argentina, and also because of all her research done, with many papers published, and discovering of different species of freshwater fishes in Argentina. Now, I would like to talk about one way of studying this freshwater ecosystems. We can determine the water quality of these ecosystems by a system based on indexes. So there are different types of indexes of water quality, for example, physical and chemical indexes, or biological indexes. I would like to talk about one of the biological index, to see an example of how they work. So I would like to talk about this index called BMWP, which is a procedure for measuring water quality depending on the families of macro-invertebrates that we can find in these waters, and using them as biological indicators. So the method of the BMWP is based on the tolerance to organic pollutants. Basically, the idea is that there are some macro-invertebrates like maize flies that for instance, indicate clean waters. So that they are given a tolerance score of 10. But the lowest scoring invertebrates are invertebrates like worms from the oligochaeta family, which score around one. So that the presence of different types of macro-invertebrates will indicate different values of the score, and finally, different values of their indexes indicating if the waters are with higher values of quality, or lower values of quality water. So the highest the value, the cleanest the water is. Finally, I would like to introduce a limnologist, Kathleen Carpenter. Who published the first British textbook on freshwater ecology that is called Life in Inland Water. Her research was mainly focused on the effects of metal mining pollution in the freshwater ecosystems, and concretely, in fishes and macro-invertebrates. I would like to end this video, just considering this work of Kathleen Carpenter, because she gave us an example of the importance of the studies of the global change drivers into freshwater ecosystems, to try to understand our contemporary world.
