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Bayesian Applications
Published in Song S. Qian, Mark R. DuFour, Ibrahim Alameddine, Bayesian Applications in Environmental and Ecological Studies with R and Stan, 2023
Song S. Qian, Mark R. DuFour, Ibrahim Alameddine
Although many applications of change point models are focused on detecting changes over time, we can use change point models in many ecological applications to model the changes of various aspects of an ecosystem along environmental gradients. As reasoned in Richardson et al. [2007], an ecosystem can withstand a certain level of disturbance (e.g., increased level of pollution) without losing the system's function and service. As the disturbance intensifies, an abrupt change of the ecosystem may occur, often in the form of rapid transition from the previous stable state to an alternative stable state once the disturbance exceeds a threshold. In our Everglades example in Chapter 6, we mentioned that bladderworts (Utricularia spp.) are a keystone species of the Everglades wetland. It provides structure support to form the characteristic periphyton mat community of the Everglades wetland ecosystem. We used the stem density in the experimental mesocosm as a measure of the species response to increased phosphorus concentrations. The floating plant uses free CO2 in the water for photosynthesis. As phosphorus concentration increases, algal photosynthesis uses aqueous CO2 leading to increased pH level during the day. High pH levels are linked to low levels of free CO2. Increased algal growth prevents bladderwort photosynthesis during the day. The abrupt change in bladderwort stem count density along a TP gradient is very similar to the abrupt change in Neuse River TP over time (Figure 7.15).
Hydrobiological Evaluation of Side Effects of Larvicide Treatments Against Simulium Damnosum
Published in Max J. Miller, E. J. Love, Parasitic Diseases: Treatment and Control, 2020
More than 500 lotic taxa have been identified from Ivory Coast. They seem to be present in equal abundance in treated and untreated rivers. The medium-term application of an organophosphate insecticide could be regarded as an excessive input of nutrient, which could lead to an abnormal growth of periphytic and planktonic algae. However, no observations have been made which would confirm this hypothesis. While occurrence of a thick and localized coverage of algae appears from time to time in the rivers, it occurs in untreated as well as in the treated areas.
Organic Matter
Published in Michael J. Kennish, Ecology of Estuaries Physical and Chemical Aspects, 2019
Measurements of benthic microalgal production have been compiled for a number of estuaries (Table 4). These measurements are comparable to those of phytoplankton, but lower than production estimates of salt marsh grasses, seagrass meadows, and mangroves. A major part of the primary production in tidal flats often has been ascribed to littoral microphytobenthos. Epiphytic algae growing on the leaves of Zostera, Thalassia, Ruppia, and other seagrasses in subtidal waters supply periphyton, a rich source of food for many heterotrophs. A diverse assemblage of epibenthic and epiphytic diatoms, dinoflagellates, filamentous algae, euglenoids, and blue-green algae can play a crucial role in salt marsh biotopes, contributing significantly to the total primary production of certain marsh systems.22 For example, the microalgal productivity in salt marsh systems of Massachusetts139 and Georgia22,113 amounts to nearly 25% of the aboveground grass production for the marshes. Long and Mason,140 reviewing primary production of salt marshes in general, reveal a net productivity by algae equal to about 20% of the total, with the algal production being largely confined to unvegetated areas (e.g., salt pans and creek banks) or marsh flats.
Toxicity of the herbicides used on herbicide-tolerant crops, and societal consequences of their use in France
Published in Drug and Chemical Toxicology, 2022
The photosynthetic potential of the cyanobacteria Microcystis aeruginosa suffered 29 and 14% decreases after 16 h exposure to 67 μg/L of the IMI imazethapyr and 3 μg/L of the SUL metsulfuron-methyl (MSM), respectively, and that of the algae Selenastrum capricornutum presented a 27% decrease after exposure to 3 μg/L of MSM (Peterson et al. 1994). The SUL nicosulfuron had an impact on algal community diversity (it inhibited diatoms more than chlorophytes) and on the photosynthetic yield at a concentration of 30 μg/L (Seguin et al. 2001). SUL herbicides affected growth and reproduction of Chlorella fusca at concentrations between 0.08 and 1.2 ppm (Fahl et al.1995), and those of Scenedesmus acutus at about 0.1 ppm (Grossmann et al.1992; Sabater and Carrasco 1997). SUL herbicides could inhibit the incorporation of adenine and thymidine of periphyton communities from natural creeks for concentration as little as 3 nM (Nyström et al. 1999).