The importance of competitor identity,morphology and ranking methodology to outcomes in interference competition between sponges

The nature or structure of competition within communities has been a dynamic area of practical and theoretical research for a number of decades. Certain components of some communities have proved hard to incorporate within such studies; in marine benthic work this has included the sponges. In this study, intra- and inter-phyletic interactions involving sponges (7,817 in total) were studied on 125 rocks (ranging in surface area from 10 to 2,438 cm ²) at a site experiencing low disturbance levels at Lough Hyne Marine Nature Reserve, Co. Cork, Ireland. The outcomes of sponge-sponge (intra-phyletic) interactions were significantly different in both outcome and structure to those involving sponges and representatives of other phyla. Typically sponge-sponge competition resulted in a much higher number of tied outcomes than did inter-phyletic encounters. Sponges over-grew all groups of organisms with the exception of some cnidarians and ascidians. The morphology of any sponge species (thickness in most cases) was important in determining the outcome of intra-phyletic, but not inter-phyletic, interactions. Sponges which exhibited thick (>2 mm) crusts were, in the majority of interactions, superior competitors compared to the thin (<1 mm) crusts. However, the method used to rank species (i.e. wins:loss or wins:total ratio) made a significant difference to the ranking of sponge competitors. The transitivity of the sponge assemblage investigated was calculated using the index formulated by Tanaka and Nandakumar (1994) as 0.23, indicating the assemblage to be organised as a network rather than a hierarchical system. We suggest this network of principally tied outcomes (due to standoffs) may be maintained in part by chemical interaction. However, in the absence of disturbance, the network is more likely to be mediated through processes of growth and regression of tissues during summer and winter months respectively.     

Calcification in the staghorn coral Acropora acuminata: Variations in apparent skeletal incorporation of radioisotopes due to different methods of processing

Pieces of branch from the staghorn coral Acropora acuminata were incubated with ⁴⁵CaCl₂ and NaH¹⁴CO₃ under identical conditions in the light or in the dark. Specimens were then processed in different ways. All specimens were placed in N KOH to digest tissues. Some were placed in KOH immediately after incubation; others were placed in KOH after 2 h washing, or after 2 h extraction with methanol-chloroformwater. Specimens were washed in running fresh water or running seawater; some were killed in liquid N₂ before washing. Radioactivity associated with skeleton and tissues was determined. The method of processing profoundly affected the results. In dark incubations, there was up to a four-fold difference in apparent skeletal incorporation of ⁴⁵Ca⁺⁺ between average values obtained for the different treatments. For ¹⁴C incorporation, there was a difference of up to 2.5 times. In light incubations, skeletal incorporation of both radioisotopes showed a two-fold difference between high and low average values obtained for the different treatments.     

Trauma and short-fuse weather warning perceptions

The purpose of this research was to assess the importance of psychological trauma in understanding reactions to short lead time weather warnings. The research consisted of two case studies, one in Denver, Colorado and the other in Austin, Texas. A total of 61 individuals with 9 or greater traumas were compared to 281 non-trauma exposed individuals. Results demonstrated significant differences on questions related to general beliefs about flash floods and warning perceptions as well as reported anticipated actions during a flash flood at home. Results suggest high trauma exposure may lead to more threat sensitivity and a higher probability of initiated action in a home-based flash flood.     

The role of metabolic nitrogen in coral calcification

When pieces of the staghorn coral Acropora acuminata are incubated with ¹⁴C-urea, the label is incorporated into skeletal carbonate. Incorporation of this label differs from that of H¹⁴CO ₃ ^- , suggesting urea is not immediately hydrolysed to provide a further source of HCO ₃ ^- . The effects of certain organic substrates upon calcification suggest the ornithine cycle is involved. Citrulline, an ornithine cycle intermediate, is found in high concentrations in the tissues of hermatypic corals. Urea, allantoins, NH₃ and arginine are also present. These compounds are barely detectable in zooxanthellae or an ahermatypic coral. The allantoins may be present as calcium salts. It is suggested that allantoins are the medium by which Ca²⁺ and CO₂ are transported to sites of calcification. Hydrolysis of urea, formed by breakdown of allantoins, yields CO₂ and NH₃. The NH₃ may neutralise protons formed during precipitation of CaCO₃ and bring about their removal from sites of calcification. As well as providing urea, the ornithine cycle may also be involved in the removal of NH₃ from sites of calcification.     

Vertical migration strategies with respect to advection and stratification in a semi-enclosed lough: a comparison of mero- and holozooplankton

Patterns of zooplankton vertical movement are often difficult to interpret because of multiple, complex and confounding environmental factors. Behavioural adaptations to these environmental variables are compared within and between the holo- and meroplankton constituents of a community. We used a nested design to analyse patterns at several scales in time; (semi-diel, diel, spring-neap tidal cycle and season) and two in space; (depth and site). To reduce complexity and aid interpretation we studied a semi-isolated community in a semi-enclosed, seasonally stratified sea lough (Lough Hyne Marine Nature Reserve, Ireland). In this, the main environmental gradient was water flow rate (or water residence time) caused by tidal currents. Vertical profiles of abundance showed that populations of the most abundant species of holo- and meroplankton in the lough have considerable behavioural plasticity, enabling them to switch between sedentary and migratory behaviour and patterns of migration. Some species migrate vertically in synchrony with diel cycles and others in response to semi-diel tidal currents; a few do both, but the majority did neither. It is suggested that water column structure and hydrographic discontinuities caused by flow rate and pycnocline dynamics are responsible for the variable patterns of vertical migration and distribution.Communicated by J.P. Thorpe, Port Erin     

Trauma and short-fuse weather warning perceptions

The purpose of this research was to assess the importance of psychological trauma in understanding reactions to short lead time weather warnings. The research consisted of two case studies, one in Denver, Colorado and the other in Austin, Texas. A total of 61 individuals with 9 or greater traumas were compared to 281 non-trauma exposed individuals. Results demonstrated significant differences on questions related to general beliefs about flash floods and warning perceptions as well as reported anticipated actions during a flash flood at home. Results suggest high trauma exposure may lead to more threat sensitivity and a higher probability of initiated action in a home-based flash flood.