The Effects Of Reduced Salinity On Colonial Growth And Membership In A Hydroid

The effect of different salinity levels on colonial growth and gonozooid frequency of the hydroid Campanularia flexuosa Hincks has been studied. It is shown that the usual cumulative presentation of growth data tends to obscure evidence of acclimation and other features of importance to an interpretation of adaptations of the growth process to salinity changes. A method of analysis is described that not only demonstrates acclimation, but apparently shows how growth is controlled after disturbance by changes in salinity. One other response to reduced salinity and other unfavourable changes in water chemistry is an increase in gonozooid frequency due to the diversion of resources from the formation of new hydranths.

Benthic megafauna and CO2 bubble dynamics observed by underwater photography during a controlled sub-seabed release of CO2

In 2012, a controlled sub-seabed release of carbon dioxide (CO2) was conducted in Ardmucknish Bay, a shallow (12 m) coastal bay on the west coast of Scotland. During the experiment, CO2 gas was released 12 m below the seabed for 37 days, causing significant disruption to sediment and water carbonate chemistry as the gas passed up through the sediment and into the overlying water. One of the aims of the study was to investigate how the impacts caused by leakage from geological CO2 Capture and Storage (CCS) could be detected and quantified in the context of natural heterogeneity and dynamics. To do this underwater photography was used to analyze (i) the benthic megafaunal response to the CO2 release and (ii) the dynamics of the CO2 bubble streams, emerging from the seabed into the overlying water column. The frequently observed megafauna species in the study area were Virgularia mirabilis (Cnidaria), Turritella communis (Mollusca), Asterias rubens (Echinodermata), Pagurus bernhardus (Crustacea), Liocarcinus depurator (Crustacea), and Gadus morhua (Osteichthyes). No discernable abnormal behavior was observed for these megafauna, in any of the zones investigated, during or after the CO2 release. Time-lapse photography revealed that the intensity and presence of the CO2 bubble plume was affected by the tides, with the most active bubbling seen at low tides and the larger hydrostatic pressure at high tide suppressing CO2 bubbling from the seabed.