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That ecological and evolutionary processes can take place on the same time scale is a recent insight. Today we also know that they are directly linked to each other. In the lake Tåkern, in year 2000, there was a structural change when phytoplankton declined and submerged vegetation, mainly stoneworts began to spread. This led to evolutionary changes in the aquatic sowbug, Asellus aquaticus which had previously been limited to the reed, most likely feeding on detritus. But then, sowbugs could exploit the new habitat in stoneworts and a new food resource in terms of periphyton. The aim of this study was to investigate whether the differentiation of the populations has led to specialization in the ecological roles of sowbugs as shredder of coarse detritus and grazer of periphyton. The study was a laboratory experiment in which groups of sowbugs were feeding on decomposing alder (Alnus glutinosa) leaves or periphyton growing on tiles. The results showed that there was no specialization in the habitat-specific food. However, reed animals had a greater (31 %) grazing effect than the stonewort animal on periphyton. There was also a non-significant tendency for reed animals to consume more leaves than the stonewort animals. The conclusion is that the different populations are not different in their functional roles, but the reed animals consume approximate 25 % more food than the stonewort animals, possibly because of higher activity.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1994. / Includes bibliographical references (leaves 102-123). / Microfiche. / xiii, 123 leaves, bound ill. (some col.) 29 cm

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2005. / Härtill 6 uppsatser.

Thesis (Ph.D.)--Memorial University of Newfoundland, 2002. / Bibliography: leaves 116-135.

Thesis (M.S.)--Ohio University, November, 2003. / Title from PDF t.p. Includes bibliographical references (leaves 61-68)

Sponges have important ecological functions on coral reefs because they are regionally abundant, competitively dominant, and process large volumes of seawater. The sponge loop hypothesis proposes that sponges consume dissolved organic carbon (DOC) and then releases the carbon as shed cellular detritus back to the reef benthos. Within this context, we examined the carbon flux mediated by the giant barrel sponge, Xestospongia testudinaria, on reefs in the Red Sea, where sponge abundance is comparatively low relative to coral reefs elsewhere, such as the Caribbean. Seawater samples were collected from the incurrent and excurrent (In-Ex) flow of 40 sponges from inshore, mid-shelf, and offshore reefs between 18° and 22°N latitude off the coast of Saudi Arabia. Concentrations of DOC and living particulate organic carbon (LPOC) were significantly higher in incurrent (ambient) seawater on inshore reefs than mid-shelf and offshore reefs. Consistent with studies of X. muta in the Caribbean, the diet of X. testudinaria is comprised primarily of DOC; mean values of the nutritional components across all sites were 60.5% DOC, 35.7% detritus, and 3.8% LPOC. Taking into account the specific filtration rates of nutritional components and oxygen consumption of sponges across the inshore-offshore gradient, there is evidence (1) of a threshold concentration of DOC below which sponges cease to be net consumers of DOC, and (2) that sponges on offshore reefs are food-limited. Contrary to the sponge loop hypothesis, there was no evidence that X. testudinaria, returned DOC to the benthos in the form of detritus, but was, instead, a net consumer of detritus from the water column. Unlike the cryptic, interstitial sponges that were studied to advance the sponge-loop hypothesis, emergent sponges may have an alternate pathway for returning DOC to the benthos by converting it to sponge biomass rather than sponge detritus.

The goals of this study were 1) to integrate several aspects of detrital dynamics with the composition and production of shredder populations and 2) to present evidence of a shredder regulatory role in headwater strewn detrital dynamics. The importance of leaf shredding aquatic insects (shredders) in the breakdown of leaf detritus and production of particulate organic matter (POM) was evaluated in three permanent and three temporary southern Appalachian headwater streams. Shredder population dynamics were compared to several stream detrital parameters: CPOM breakdown rates, POM concentrations, average POM particle sizes, and POM transport. In general, permanent streams with the greatest shredder densities, biomass, and annual production rates had the fastest leaf breakdown rates, highest low-flow POM concentrations, largest average POM particle sizes and greatest POM transport estimates. Temporary stream environments depressed shredder populations resulting in a reduction of detrital processing and POM transport. Microbial activity, stream velocity, base-flow discharge, and water temperature did not correlate with detrital parameters for comparisons between permanent and temporary streams. Shredder contribution to total benthic CPOM breakdown in the six study streams ranged from 31% in a permanent stream to 1% in a temporary stream. / Ph. D.

Thesis (Ph. D.)--University of Hong Kong, 1989.

This project addressed if decaying macroalgae and leaf detritus play a major role in the detrital pool of a 7th-order karst riverine system. Decay rates, macroinvertebrates colonization patterns, and change in δ13C values of Cladophora, Platanus occidentalis, and a mix of Acer negundo and A. saccharinum were tracked during summer and autumn months for portions of multiple years. Packs of air-dried Cladophora, Acer, and P. occidentalis were placed in mesh bags and put in groups (n=4) in wire baskets. Seven baskets were submerged in riffle (0.5 m) and deeper run (2 m) habitats. Benthic organic matter was collected with each pack to see if there was a correlation with δ13C signatures of decaying macroproducers to help understand what is entering the detrital food web. Summer 2014 Cladophora and Acer were significantly faster to breakdown than Platanus in both habitats. In autumn‒spring 2014‒2015, Cladophora was significantly faster to breakdown than leaves. Isotopic values of Cladophora were not significantly different than leaves in summer 2014 but were significantly more δ13Cdepleted in the autumn‒spring 2014‒2015. There were no significant differences in macroinvertebrate abundance between the macroproducers for either season. Cladophora had significantly lower macroinvertebrate richness in both seasons, lower shredder abundance, but a significantly higher abundance of clingers. The mean δ13C values of benthic detritus were significantly different than all three macroproducers in the summer and significantly different than Cladophora in the run treatment for autumn‒spring. Seasonality had a strong influence on breakdown rates, leading to greater mass loss of all three species in the warm summer months compared to the cooler autumn‒spring months. The low macroinvertebrate richness and shredder abundance on the decaying macroalga suggests Cladophora may not be consumed by macroinvertebrates but used strictly as habitat. The implication of rapid Cladophora decay during warm seasons, plus few colonizing macroinvertebrate taxa, is that the decaying macroalgae may not pass through a decomposer food web before being remineralized as CO2.