Temporal variation of periphyton communities: a 3-year study from northwest Lake Simcoe, Ontario, Canada

Periphyton composition, density, and diversity (Shannon-Wiener index), as well as thickness of periphyton communities developed on glass coupons, were studied from nearshore areas of northwest Lake Simcoe, Canada, during 2009, 2010, and 2011. The objective of this study was to quantify the temporal (yearly) changes in periphyton occurring in the littoral zone of Lake Simcoe and identify water quality variables that may be driving periphyton community dynamics. Clean glass slides were suspended at 0.5 m below the surface waters and retrieved on multiple days after suspension. The retrieved glass slides were immediately analyzed under a microscope to observe periphyton genera composition, density, diversity, and biofilm thickness. While the number of genera, diversity, and biofilm thickness showed significant variation among years of observation, the density did not. In all 3 years, Bacillariophyta were the dominant group, while Chlorophyta, cyanobacteria, and Chrysophyta were routinely represented in the periphyton community. A periphyton community dominated by Navicula and Gomphonema in 2009 changed to Achnanthidium and Cocconeis in 2010, which subsequently changed to Achnanthidium and Navicula (all belonging to Bacillariophyta) in 2011. The density of periphyton was significantly related to biofilm thickness across all 3 years. Principal component analysis on periphyton genera composition and abundance showed variation among years. Regression analysis suggested the shift in the number of genera was related to the variation in total phosphorus and dissolved oxygen concentrations in the water. Long-term data on periphyton community dynamics will prove useful to devise a periphyton-based water quality index for northwest Lake Simcoe

In situ hatching of invertebrate diapausing eggs from ships’ ballast sediment

Ships that enter the Great Lakes laden with cargo carry only residual ballast water and sediment in ballast tanks. These ships are designated ‘no ballast on board’ (NOBOB) and constitute > 90% of inbound traffic. We conducted in situ experiments using emergence traps to assess the viability and the introduction potential of invertebrate diapausing stages present in ships’ ballast sediment. All trials commenced while vessels operated on the lower lakes (Erie, Ontario) and were completed 6–11 days later at ports on the upper lakes (Michigan, Lake Superior). Eight trials were conducted on four ships using five different ballast sediments. Hatching was observed on every ship, although not from all sediments on all ships. Overall hatch rates were very low (0.5 individuals per 500 g sediment), typically involving activation of < 0.05% of total eggs present. Five species of rotifers and copepod nauplii were hatched from ballast sediments, although only one or two species typically hatched from any one sediment. Results of this study indicate that hatching of diapausing eggs contained in ballast sediment of NOBOB ships poses a relatively low risk of invasion to the Great Lakes. However, as reproduction may occur in tanks, and non-indigenous species may be involved in numerous introduction events, the risk posed by this vector is small but potentially important. While dormancy is a characteristic enabling enhanced survival during transportation in ballast tanks, it becomes a hindrance for introduction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72804/1/j.1366-9516.2005.00150.x.pd

Sessile Organisms on PVC Panels in the Waters around a Coral Reef of Ishigaki Island, Yaeyama Islands, Japan, Immediately after the Catastrophic Coral Bleaching in 1998

Sessile organisms on PVC panels suspended inside and outside coral reef at Ishigaki Island, Yaeyama Islands, Japan, was monitored for 20 days just after the wide-spread incident of coral bleaching in September, 1998. The settlement of a total of 16 species of algae and invertebrates was recorded. Generally, Enteromorpha sp. (Chlorophyceae) dominated the panels. The percentage area cover, number of species, biomass and algal growth were significantly greater in waters outside the reef

In Vitro Laser Ablation of Natural Marine Biofilms

We studied the efficiency of pulsed low-power laser irradiation of 532 nm from an Nd:YAG (neodymium-doped yttrium-aluminum-garnet) laser to remove marine biofilm developed on titanium and glass coupons. Natural biofilms with thicknesses of 79.4 ± 27.8 μm (titanium) and 107.4 ± 28.5 μm (glass) were completely disrupted by 30 s of laser irradiation (fluence, 0.1 J/cm(2)). Laser irradiation significantly reduced the number of diatoms and bacteria in the biofilm (paired t test; P < 0.05). The removal was better on titanium than on glass coupons