Effects of herbivorous gastropod grazing on the sedimentation and succession of subtidal macroalgal assemblages

The subtidal zone on cold temperate rocky coasts is an environment exposed to much less physical disturbance than the intertidal, and sediment deposition is continuous. Removal of this sediment by gastropod grazers is therefore presumed to affect the structure of subtidal algal communities. This concept was investigated by evaluating the grazing effects of the dominant herbivorous gastropod Omphalius rusticus by exclusion experiments in the field. Settlement plates of both exclusion and control treatments were placed every month from November 2014, and immersed for 1 mo. Algae colonized from May and tended to increase in biomass toward summer. No marked differences were observed in the algal composition of exclusion and control. Sediment deposition showed no apparent seasonal changes. Cumulative successional plates of both exclusion and control treatments were placed in November 2014, and immersed for 1 to 9 mo. The colonization of algae started in February and the species number peaked earlier in the exclusion and later in the control. Sediment load and algal biomass were high from February to May in the exclusion, and from April to July in the control. Seedlings of Sargassum confusum were found in both plots starting in July. We conclude that O. rusticus constantly removed sediments by its grazing activity and had a large impact on the formation of the macroalgal community by controlling sediment deposition. Its presence delayed the colonization of early-successional turf algal species, but did not affect colonization of late-successional canopy-forming algae such as S. confusum.

Domestication via the commensal pathway in a fish-invertebrate mutualism

Domesticator-domesticate relationships are specialized mutualisms where one species provides multigenerational support to another in exchange for a resource or service, and through which both partners gain an advantage over individuals outside the relationship. While this ecological innovation has profoundly reshaped the world’s landscapes and biodiversity, the ecological circumstances that facilitate domestication remain uncertain. Here, we show that longfin damselfish (Stegastes diencaeus) aggressively defend algae farms on which they feed, and this protective refuge selects a domesticator-domesticate relationship with planktonic mysid shrimps (Mysidium integrum). Mysids passively excrete nutrients onto farms, which is associated with enriched algal composition, and damselfish that host mysids exhibit better body condition compared to those without. Our results suggest that the refuge damselfish create as a byproduct of algal tending and the mutual habituation that damselfish and mysids exhibit towards one another were instrumental in subsequent mysid domestication. These results are consistent with domestication via the commensal pathway, by which many common examples of animal domestication are hypothesized to have evolved.

The Effects of Effluent Discharged from Bottling Companies on Algal Composition in Kakuri Stream Kaduna, Nigeria

This study determined the impact of soft drink effluent on algal composition in Kakuri stream, Kaduna South Local Government Area, Kaduna. Limnological studies of soft drink effluent were carried out for a period covering wet and dry seasons across three (3) sampling points code-named Stations A, B and C. Some physio-chemical parameters were analysed using standard methods. A total of 43 species were observed belonging to 5 families. Chlorophyceae and Cyanophyceae were the most abundant families across the three (3) stations. The total flora count was high during the dry season, 1965 cells than wet season, 1071 cells. The most dominant species were Euglena sp., Microcystis sp. and Oscillatoria sp. The pH of the three stations was more alkaline (pH 8.1) but reduces slightly at stations B and C during the months of May (pH 5.2) and August (pH 6.5). The biological oxygen demand (BOD) was relatively high across the stations, dissolved oxygen was generally low except for some months (December at station A and January at station B) that had its dissolved oxygen values above 5.00 mg/l. Euglenophyceae showed positive correlation to conductivity and BOD, Chlorophyceae was positively correlated with BOD, Cyanophyceae showed positive relationship with BOD and dissolved oxygen, Charophyceae was positively correlated with dissolved oxygen, Bacillariophyceae showed positive correlation with pH, temperature, phosphorus, BOD and dissolved oxygen. Effluent discharge and farmland run-off passed into the water body supports growth of dominant species indicating organic pollution, thus, poses a threat to the environment over a long period of time. Keywords: Algae, Effluent, Biological oxygen demand, Dissolved oxygen.

Effects of CeO2 nanoparticles on the algal composition and photosynthetic activity of phototrophic biofilm

The influences of CeO2 nanoparticles (NPs) on phototrophic biofilm were explored in terms of the algal composition and photosynthetic activity. Biofilms were cultivated in an artificial flume and exposure experiments were conducted with two levels of CeO2 NPs (0.05 and 0.5 mg/L) for 10 days. Results showed that 0.05 mg/L CeO2 NPs treatment altered the algal composition of biofilms, while the total Chl a and the photosynthetic activity maintained at the similar level as the control test. 5 mg/L CeO2 NPs not only changed the algal composition of biofilms, but also significantly decreased the photosynthetic activity, suggesting that high concentration of CeO2 NPs might lead to serious consequences to the primary production and nutrient cycling in aquatic environments.

Blooming algae: a Canadian perspective on the rise of toxic cyanobacteria

Algal bloom reports are on the rise across Canada. While eutrophication is the main driver, other stressors of aquatic ecosystems, specifically climate change and food web alterations from the spread of invasive species and overfishing, are compounding factors acting in concert or independently. Current models can predict the average algal and cyanobacterial biomass concentrations across temperate lakes as a function of nutrients, but models to specifically predict harmful algal composition and toxicity are lacking. At the within-lake scale, where management occurs, strong year to year variations in cyanobacterial blooms remain challenging to explain, let alone predict. The most common cyanotoxins, the hepatotoxic microcystins, are chemically diverse with some variants more toxic than others and with greater propensity for persistence and bioaccumulation. These differences have been largely overlooked, as current guidelines have been based on microcystin-LR, considered the most common variant. Microcystin-LA is also encountered in Canadian waters and appears to exhibit greater persistence and bioaccumulation. With cyanobacterial blooms most likely to increase across the country, including the north, guidelines and policies for cyanotoxins in drinking and recreational waters as well as fish will need to be developed for the protection of ecosystem and human health. Ultimately, control of eutrophication is the most important option for managing toxic cyanobacterial blooms; nitrogen and phosphorus need to be considered as environmental contaminants, as both play a role in controlling the dominance of toxigenic cyanobacteria.