Decomposition and nutrient liberation rates of plant material in the Parana medio River (Argentina)

The degradation of plant material was studied in order to obtain degradation coefficients and nutrient release kinetics of the vegetation that will be submerged during the filling of the future Parana Medio man-made lake. A group of 13 plant species representative of the whole vegetation of the area were chosen.The plant samples (submerged at 2.5–4 m in the Setubal lagoon), were periodically analyzed during 97 days. The experimental data were fitted to an exponential decomposition model. The plants were classified according to their velocities of degradation into three groups: fast (K>0.01), mean (0.01>K>0.005) and slow (K<0.005). The curves of release of P, N, Ca, Mg, Na and K in function of time are presented and discussed.     

The planktonic rotifers of the estuarine lagunar complex of Suape (Pernambuco,Brazil)

We studied spatial and temporal distribution, abundance, diversity, equitability and species associations of the rotifers of the estuarine area of Suape (Pernambuco-Brazil), based on plankton samples collected according to the tidal regime at 11 fixed stations in Suape Bay and the estuaries of Massangana, Tatuoca and Ipojuca Rivers, during February (dry season) and July (rainy season) of 1978. Concurrent hydrological and climatological data were taken. Eight species groups were established. In general, rotifers dominated in the Ipojuca River estuary and stations subject to its influence. Greatest community similarities were observed among nearby stations, during the same tide and season. Hydrological factors influenced the occurrence and distribution of some species, and a close correlation between phytoplankton and rotifers was observed. Pollution in Ipojuca River contributed to diversity.     

Sphagna of the 1979 Projeto Flora Amazônica expedition

Within the great expanse of the Brazilian Amazon Basin,Sphagnum has been greatly overlooked, in part because of its scarcity and in part because of the paucity of trained bryological collectors in the area. During a Projeto Flora Amazônica expedition in 1979, seven specimens ofSphagnum were collected, representing six species, five of which are newly described:S. amazonicum, S. dimorphophyllum, andS. subsecundoides in sectionSphagnum;S. curicuriariense andS. ripense in sect.Subsecunda. Also discussed areS. negrense Mitt. andS. sanguinale Warnst.     

Weeds of Kentucky and Adjacent States. A field guide. By Patricia Dalton Haragan The University Press of Kentucky, Lexington, KY 40506-0336

In 1843 S. B. Buckley (1809–1884) traveled up the St. Johns River, Florida in search of plants, shells, and possibly other natural history objects. Buckley encountered many difficulties in interior Florida and his trip did not live up to his original expectations. It was unfortunate that the took years to distribute his plant specimens, since few botanists or naturalists had preceded him into that poorly explored region.     

The dilution and loss of wetland function associated with conversion to open water

Some degree of wetland loss characterizes most coastal systems of the United States. This loss is generally reported as a decrease in wetland area, but most coastal land loss entails wetland submergence and conversion to open water. This concurrent increase in the area of aquatic habitat decreases the wetland:open water ratio, effectively diluting the area of remaining wetland relative to the aquatic system. The functional loss of intertidal wetlands to the ecosystem associated with this dilution effect may significantly alter ecological functions dependent on the interactive coupling of wetland and aquatic habitats. The magnitude of functional loss is strongly dependent on the wetland:water ratio of an estuary. In estuaries with open bay-type morphologies, the open water area is already large and functional loss of wetland by additional dilution may be only slightly greater than the areal wetland loss. Where estuaries are wetland-dominated, however, conversion of even a small percentage of wetland to water drastically alters the wetland:water ratio. In these cases, functional losses by dilution are much greater than the rate of areal wetland loss.In the Barataria Basin estuary, Louisiana, between 1967 and 1987, 15.4% of the salt marsh was lost (assuming a loss rate of 0.8% y^–1 of the remaining marsh). We estimated that this 15% loss of salt marsh, by conversion to open water, may have resulted in a 27% reduction in the supply of inorganic nutrients and organic matter to the estuarine water column by the marsh, simply due to the dilution effects of the changed wetland:open water ratio. Functional losses of this magnitude may have serious implications to the estuarine ecosystem where intertidal wetlands support aquatic productivity by exporting nutrients and energy or where intertidal wetlands buffer aquatic eutrophication by importing excess nutrients and organic matter. It is conceivable that an estuary characterized by wetland loss may reach a point where, although some wetland remains, its functional value to the ecosystem is essentially gone.     

Dynamics of carbon assimilation by St Lawrence estuary phytoplankton at the end of summer

This study presents data of in situ measurements of inorganic carbon assimilation by phytoplankton communities of the St Lawrence estuary during the end of summer 1982. We used carboxylase activity measurements (ribulose-1,5-bisphosphate carboxylase, carboxylases) and the ¹³C/¹²C ratio of phytoplankton organic carbon, expressed as ¹³C, to study patterns of assimilation. Upper estuary phytoplankton communities showed a smaller turn-over rate in carbon assimilation than lower estuary phytoplankton communities. Carbon assimilation was limited by light intensity in the upper estuary and by CO₂ availability in the lower estuary. In the St Lawrence estuary, stable carbon isotope ratios of phytoplankton organic carbon seemed to be controlled by inorganic carbon availability rather than by phytoplankton metabolism.     

Intraspecific resource partitioning in a headwaters stream fish,the pearl dace Semotilus margarita (Cyprinidae)

Synopsis Pearl dace, Semotilus margarita, are common in slow-moving channels and pools of the headwaters of the Brokenhead River. From May to September age groups 0, 1 and 2+ were partially segregated in space based on water depth with age 0 occupying shallow pools and shallow channels. Age 1 were abundant in shallow pools and deep channels while age 2+ occurred in deep channels and deep pools. In November all age groups coexisted in deep pools. Pearl dace are omnivorous consuming invertebrates, plant material, and detritus. From May to September age groups 0 and 1 consumed mainly terrestrial invertebrates (Diptera, Hymenoptera, Thysanoptera) but age 1 consumed more detritus than age 0. Age 2+ consumed mainly aquatic Diptera larvae. Although all ages consumed aquatic insects almost exclusively in November differences in diet between age groups still existed. Younger fish fed higher in the water column than older fish. Intraspecific resource partitioning of food and space occurs between age groups and this combined with the omnivorous diet is highly adaptive to the headwaters of streams.     

Full-sib and reciprocal recurrent selection in relation to pearl millet improvement

Summary During the years 1973 to 1976 two populations of Pearl millet with wide genetic base, namely, Delhi composite (DC) and Vijay composite (VC) were used to compare the response to selection by the full-sib family method from biparental material and reciprocal recurrent selection (RRS). The results indicated that it was possible to advance grain yield with one cycle of RRS by about 23 percent in the case of population DC and 21 percent in population VC, while for the full-sib selection method, the improvement in grain yield was not so rapid. The studies on the nature of gene action indicated that both additive and dominance gene actions were important for grain yield, ear length and ear girth. The coefficient of variation as a result of RRS was reduced in population DC, while it was comparable to base population in the other population. The correlation studies indicated that the magnitude of favourable correlation of different characters with grain yield were higher in case of RRS compared to the full-sib system. The presence of negative correlation of plant height with grain yield in both the improved populations indicated the possibility of breakage of unfavourable gene combinations through RRS and full-sibs developed from biparental mating.