Dormant propagule banks of aquatic invertebrates in ponds invaded by exotic pine species in southern Brazil

Exotic pine invasion affects native wetland communities in the Southern Hemisphere by changing the hydrological regimen and physicochemical characteristics. Studies evaluating the emergence of aquatic invertebrates from dormant stages are vital to identify the resilience of aquatic communities in ponds invaded by exotic pine species. In the present study, we tested the hypotheses that: (1) pine invasion decreases the richness of drought-resistant aquatic invertebrates in ponds; (2) pine invasion modifies the invertebrate composition in ponds; and (3) these differences in species composition (β diversity) are associated primarily with species turnover. Dry sediment samples were collected from three natural ponds in native grassland and three ponds in a pine invasion matrix in southern Brazil. In all, 7205 invertebrates, primarily represented by cladocerans (18 species), were sampled after rewetting dry sediments. Pine invasion decreased the richness of aquatic invertebrates because the natural ponds had almost 60% more species and a higher number of estimated species than the pine ponds. The composition differed between natural and pine ponds, and this difference in species composition (β diversity) was associated primarily with the replacement of some species by others. The presence of pine appears to alter colonisation and survival rates of aquatic invertebrates that aestivate in dry sediments in southern Brazil wetlands.

Linear Alkylbenzenes (LABs) in Urban Riverine and Coastal Sediments and Their Usefulness as a Molecular Indicator of Domestic Wastes

Linear alkylbenzenes (LABs) and linear alkylbenzenesulfonates (LAS) were measured in river and coastal (bay) sediments in Tokyo metropolitan area. LABs are widely distributed in the sediments with concentrations of a few µ g/g-dry sediments. LAS contents in sediments are extremely low in Tokyo Bay (~ 0.01µg/g) as compared with those in the rivers (hundreds µg/g). This fact indicates the higher persistency of LABs in the riverine and coastal sediments. The progressive relative depletion of external isomers (in which the phenyl group is attached near to the end of the alkyl chain) was observed on going from the source (i.e. LABs in commercial LAS-detergents) to Tokyo Bay sediments. An incubation experiment substantiated that the isomeric change of LABs is caused by selective microbial degradation. The I/E ratio (ratio of [6-C12 AB + 5-C12 AB] relative to [4-C12 AB + 3-C12 AB + 2-C12]; n-Cm : n indicates the position of substitution of phenyl group to alkyl chain and m indicates the number of carbons in the alkyl chain) was proposed as an index of LAB degradation. I/E ratio of LABs in Tokyo Bay sediments indicates the degree of degradation of LABs to be 50 % at most.