Periphyton on natural substratum in jurumirim reservoir (São Paulo, Brazil): Community biomass and primary productivity

Seasonal variation in the biomass and primary productivity of the periphyton on natural substratum (internodes of Echiiwchloa polystaclya HBK Hitch.) was studied during one year (from August 1993 to July 1994) in a lagoon with permanent connection with a river. We also analysed the relationships between the hydrological regime, climatic conditions and physico-chemical variables of water with the biological compounds of the periphyton. Values of dry mass, ash-free dry mass, chlorophyll a and phaeophytin of periphyton ranged from 0.55±0.24 g m-2 to 7.86±4.93 g m-2; 0.28±0.18 g m-2 to 3.72±2.23 g m-2; 0.57±0.09 mg m-2 to 15.57±4.52 mg m-2; 0.03±0.03 mg m-2 to 4.74±3.46 mg m-2, respectively. The primary productivity of periphytic algae measured by C14 method ranged from 6.45±1.29 mg C m-2 h-1 to 52.88± 7.55 mg C m-2 h-1. The biomass showed a peak in October 1993, February and April 1994. Higher value of primary productivity was recorded in December 1993 and January 1994 and was due to the peculiar light and nutrition conditions during this period. We conclude that biomass and productivity of the community are controlled mainly by hydrological regime (fluctuations of water level). © INTERNATIONAL SCIENTIFIC PUBLICATIONS.

ESTABLISHMENT OF THE ZEBRA MUSSEL DREISSENA POLYMORPHA (PALLAS, 1771) IN LOUGH NEAGH, NORTHERN IRELAND

Five adult Dreissena polymotpha were found on the hull of a boat moored in Kinnego Marina, Lough Neagh, in November 2005; this is the first indication of their presence in this large lake. This finding initiated a survey to determine whether the zebra mussel was present throughout Lough Neagh. Forty-four settled juveniles on debris were found at twenty sites around the lough shore. As a result of these findings a more extensive study was undertaken in October 2006 to examine planktonic and settled stages. Veliger larvae were at densities of 0.0211 veligers per m(-3). Spat collectors showed settlement at six out of the seven sites sampled at a mean density of 523.76 juvenile zebra mussels per m(-2). No adult zebra mussels were found on natural substratum in the lough during the shoreline survey. However, 24 adult zebra mussels, 7.5 mm to 24 mm long, were found on the hull of a boat moored in Lough Neagh.

Temporal variation in C, N and P of the periphyton on the tropical aquatic macrophyte echinochloa polystachya (H.B.K.) hitch. In Jurumirim Reservoir (São Paulo, Brazil)

The temporal variations in C, N and P concentrations of the periphyton on the natural substratum (Echinochloa polystachya) and its relationships to the water's climatological (air temperature and precipitation), hydrodynamic (water discharge and water level), physical (temperature, transparency) and chemical variables (conductivity, total suspended solids, nitrate, nitrite, ammonia, silica, total phosphorus and orthophosphate) were evaluated in a lagoon at the Paranapanema River mouth into the Jurumirim Reservoir (São Paulo, Brazil) from August 1993 to July 1994. An amplitude variation of 2.0 m in water level was observed. Depending on to the hydrologic conditions, the lagoon presents intermediate conditions of lentic and lotic environments. The amplitude variations in C, N and P were 14.5-52.1% C DW-1, 0.5-3.2% N DW-1, and 0.03-0.4% P DW-1, respectively. The periphyton presented a decreased protein content. The environmental trophic degree appears to be decisive in chemical periphyton composition.

Size and time of day affect the response of postlarvae and early juvenile grooved tiger prawns Penaeus semisulcatus De Haan (Decapoda:Penaeidae) to natural and artificial seagrass in the laboratory

Juvenile tiger prawns (Penaeus semisulcatus De Haan and P. esculentus Haswell) show a strong association with vegetated habitats and are rarely caught on non-vegetated areas. This pattern of distribution may be caused by postlarvae selecting vegetation when they settle, or to differences in post-settlement mortality in different habitats. In this study, we examined whether the postlarvae and early juvenile stages of P. semisulcatus would distinguish between seagrass (Zostera capricorni Aschers) without epiphytes, artificial seagrass and bare substratum in the laboratory. The responses of prawns reared from the egg to different stages of postlarval and juvenile development were tested to determine whether, and when, each size class showed a response to a particular habitat. Five size classes of postlarvae (average carapace lengths [CL] of 1.2, 1.4, 1.6, 1.7 and 2.0 mm) were offered a choice between Z. capricorni and bare sand. Small size classes of postlarvae either did not respond to Z. capricorni (1.2 and 1.6 mm CL), or were more abundant on bare substratum than Z. capricorni. In contrast, the largest size classes of postlarvae (1.7 and 2.0 mm CL) were more abundant on Z. capricorni during the day but not at night. The behaviour of postlarvae changed markedly at a size of 1.7 mm CL (22 days from the first nauplius): smaller postlarvae frequently swam in the water column; 1.7 and 2.0 mm CL postlarvae spent much more. time resting on the substrate and perched on seagrass leaves. This size at which postlarvae first respond to seagrass during the day, and show mainly benthic behaviour, is similar to the size at which they are found on shallow seagrass beds in northern Australia. Large postlarvae (2.7 mm CL) and juveniles (4.1 mm CL) both were more abundant on artificial seagrass than bare sand during the day but not at night, indicating that they respond to structured habitats. When large postlarvae (2.4 mm CL) and juveniles (3.5 mm CL) were offered a choice between Z. capricorni without epiphytes and artificial seagrass, they were more abundant on the Z. capricorni, which suggests that chemical cues from seagrass may explain some of the responses of P. semisulcatus to seagrass. (C) 1997 Elsevier Science B.V.

Germination of Ocotea pulchella (Nees) Mez (Lauraceae) seeds in laboratory and natural restinga environment conditions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Composição faunística, ecologia e história natural de serpentes em uma região no sudoeste da Amazônia, Rondônia, Brasil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Facing the future: the importance of substratum features for ecological engineering of artificial habitats in the rocky intertidal

Coastal defences are proliferating in response to climate change, leading to the creation of more vertical substrata. Efforts are being made to mitigate their impacts and create novel habitats to promote biodiversity. Little is known about the effect of aspect (i.e. north–south directionality) and inclination on intertidal biodiversity in artificial habitats. Artificial and natural habitats were compared to assess the role of aspect and substratum inclination in determining patterns of biodiversity at two tidal heights (high and mid). We also compared grazing activity between north- and south-facing surfaces in natural habitats to examine the potential for differential grazing pressure to affect community structure and functioning. Results were variable but some clear patterns emerged. Inclination had no effect on biodiversity or abundance. There was a general trend towards greater taxon richness and abundance on north-facing than south-facing substrata in natural and artificial habitats. On natural shores, the abundance and grazing activity of ‘southern’ limpets (i.e. Patella depressa) was greater on south-facing than north-facing substrata, with possible implications for further range-expansion. These results highlight the importance of incorporating shaded habitats in the construction of artificial habitats. These habitats may represent an important refuge from grazing pressure and thermal and desiccation stress in a warming climate.

Facing the future: the importance of substratum features for ecological engineering of artificial habitats in the rocky intertidal

Coastal defences are proliferating in response to climate change, leading to the creation of more vertical substrata. Efforts are being made to mitigate their impacts and create novel habitats to promote biodiversity. Little is known about the effect of aspect (i.e. north–south directionality) and inclination on intertidal biodiversity in artificial habitats. Artificial and natural habitats were compared to assess the role of aspect and substratum inclination in determining patterns of biodiversity at two tidal heights (high and mid). We also compared grazing activity between north- and south-facing surfaces in natural habitats to examine the potential for differential grazing pressure to affect community structure and functioning. Results were variable but some clear patterns emerged. Inclination had no effect on biodiversity or abundance. There was a general trend towards greater taxon richness and abundance on north-facing than south-facing substrata in natural and artificial habitats. On natural shores, the abundance and grazing activity of ‘southern’ limpets (i.e. Patella depressa) was greater on south-facing than north-facing substrata, with possible implications for further range-expansion. These results highlight the importance of incorporating shaded habitats in the construction of artificial habitats. These habitats may represent an important refuge from grazing pressure and thermal and desiccation stress in a warming climate.

The comparative effects of habitat complexity on faunal assemblages of northern temperate artificial and natural reefs

Several north temperate marine species were recorded on subtidal hard-substratum reef sites selected to produce a gradient of structural complexity. The study employed an established scuba-based census method, the belt transect. The three types of reef examined, with a measured gradient of increasing structural complexity, were natural rocky reef, artificial reef constructed of solid concrete blocks, and artificial reef made of concrete blocks with voids. Surveys were undertaken monthly over a calendar year using randomly placed fixed rope transects. For a number of conspicuous species of fish and invertebrates, significant differences were found between the levels of habitat complexity and abundance. Overall abundance for many of the species examined was 2-3 times higher on the complex artificial habitats than on simple artificial or natural reef habitats. The enhanced habitat availability produced by the increased structural complexity delivered through specifically designed artificial reefs may have the potential to augment faunal abundance while promoting species diversity.