Tiny crustaceans, whose detailed analysis can only be obtained with a magnifying glass and other high-precision optical equipment, are becoming the newest indicator to evaluate subtle but consistent changes in the marine environment, especially in the intertidal region, resulting from the interference of human actions in the natural environment or even natural environmental modifications. The innovative and surprising potential instrument for evaluating the impacts of human actions on the marine environment is related to meticulous and patient research carried out for years in the Department of Zoology of the Institute of Biology (IB) at Unicamp. The research is also part of the Biota Program, an interinstitutional effort, financed by Fapesp, to catalog and measure the existing biodiversity in the State of São Paulo.
The research coordinated by biologist Fosca Pedini Pereira Leite, associate professor at the Department of Zoology at IB, deals with the observation and interpretation of the interactions of small crustaceans with the substrates where they live, as in the case of algae - particularly sargassum. With a master's degree and a doctorate from the Oceanographic Institute of the University of São Paulo, the biologist has been researching the occurrence and relationships with the substrate of small crustaceans, especially gammarid and caprelid amphipods, in different parts of the North Coast of São Paulo since 1972.
As one of the pioneers in this line of research, Professor Fosca says that the difficulties were naturally immense in the initial phase. The available equipment cannot even be compared to today's, the professionals willing to work in the area were limited and the sources of financing were reduced. But the researcher says that the effort was worth it, because it was only with the data accumulated over decades that it became possible to detect important changes in the composition and density of amphipods in the marine environment that is the subject of her research, which now also includes the participation of researchers, postgraduate students and scientific initiation students supervised by her at IB.
The researcher explains that various aspects of the interaction between amphipods and the substrates where they live, such as algae, are evaluated. “We studied, among other aspects, the architecture of algae and how it influences the density, reproduction and feeding of amphipods, both gammarids and caprelids,” she says. In terms of reproduction, for example, she highlights, differences are analyzed even in terms of the number and diameter of eggs laid by numerous species of amphipods.
“Some species reproduce by producing a greater number of eggs in more spaced periods, while others have a smaller number of eggs, but produced in a shorter period of time, in addition to the fact that the diameter also varies, which may indicate different strategies to enable coexistence in the same algae”, highlights the researcher, who pays attention to the way crustaceans reproduce. There is no larval dispersion in the reproductive process. The eggs remain in an incubation pouch (marsupium) until they hatch into the juvenile form.
One of the changes identified by Professor Fosca and her team over time is the change in species dominance. A considerable reduction in the number of individuals of a species of amphipod was observed: Amphilocus neapolitanus, which in the initial period of work, in the early 70s, was predominant on beaches in Ubatuba, which together with São Sebastião are two of the places where the study of amphipods is concentrated. researchers from Unicamp. After years, in the same marine environment, other species such as Jassa slatteryi, Hyale nigra and Stenothoe sp began to predominate. The first is a detritivorous tube species (which forms small tubes), which in the researchers' assessment may be an indicator of the greater presence of sediments in seawater, and considered resistant to pollution, resulting from human activities on the North Coast of São Paulo. in the last years. The other two species began to predominate due to a varied diet and changes in the architecture of the algae respectively.
“At the beginning of the 1970s, the North Coast was sparsely inhabited, there was not even a shadow of the real estate invasion and the flow of tourists in recent years”, notes Professor Fosca. A similar change, he points out, was observed in the case of small molluscs also associated with algae. Previously there was a greater occurrence of carnivorous molluscs, and later a greater presence of detritivores such as Bittium varium began to be identified. “Today there is a greater frequency and intensity of oil slicks in the sea on the beaches studied, which may be affecting the composition of amphipod and mollusk species”, adds the researcher, highlighting that proof of these possible anthropic impacts depends on further study.
According to Professor Fosca, greater knowledge about the diversity, density, life habits and reproductive behavior of crustacean species associated with algae is essential for putting together a monitoring plan in the region. These tiny creatures play an important role in the food chain – many fish feed on the algae they are associated with or actively prey on them.
The study of the biology of bioindicator species to characterize the ecosystem and highlight natural and anthropic modifications is, in fact, one of the objectives of the research project coordinated by the IB professor within the Biota Program, called Costão Rochoso e Fauna Associada, which integrates, in turn, the Marine Benthic Biodiversity Project, financed by the São Paulo State Research Support Foundation (Fapesp) and developed in an integrated manner by researchers from São Paulo universities.
One of the objectives of the Biota Program, to identify and record the existing biodiversity in the territory of São Paulo, including possible new species, still unknown in the scientific bibliography, is being achieved in great style by researchers from the Department of Zoology of the Institute of Biology at Unicamp. Among the more than 20 species of amphipods studied, two have not yet been properly described by Science.
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