Microfouling Studies on Experimental Test Blocks of Steel-making Slag and Concrete Exposed to Seawater off Chiba, Japan

Abstract

Microfouling studies with the emphasis on microalgae (Bacillariophyceae) were carried out on test blocks of steel-making slag in comparison with concrete. Two types of slag test blocks, with and without fly-ash as an additional source of silica, and concrete test blocks of size 75 x 26 x 26 mm were used to study microfouling build-up for a period of 30 d, with intermittent samplings after 1, 2, 3, 7, 14 and 21 d. The species composition, cell density, biomass and surface pH of the test pieces were determined, in addition to the hydrographic parameters of the water column. Microfouling studies showed higher numbers of algal species as well as a greater cell density on the slag than on the concrete blocks. This was true with respect to biomass measured as dry weight also. Colonization was significantly delayed in the case of concrete. Navicula spp. and Nitzschia spp. were the initial colonizers on all three types of substrata and were the dominant genera throughout the study period. While the number of species increased, several disappeared after colonization, as a part of community build-up. The surface pH of the slag blocks was near neutral, whilst that of the concrete was highly alkaline during the initial period of exposure. This alkaline surface reduced the rate of species colonization on the concrete blocks initially. The study showed severe biofouling on the slag blocks compared to concrete and thus they were considered an environmentally benign construction material for land protection. The use of slag as the construction material for land protection would greatly reduce the expense compared to concrete.

Epifaunal colonization of the Loch Linnhe artificial reef: Influence of substratum on epifaunal assemblage structure

“…In addition, the material from which an artificial reef is made also has the potential to have a significant affect on the way the surfaces of the reef are colonized by epifauna and flora that, in turn, will influence the eventual biodiversity of the system. Very few studies have examined epifaunal/floral colonization on artificial reefs or have compared how a range of substrata commonly used for the construction of artificial reefs are colonized by epibiota in the sub-tidal environment (but see Jensen et al 1994;Hatcher, 1997;Nandakumar et al 2003;Qiu et al 2003). Such studies are important in the assessment of how the construction material affects the final productivity of an artificial reef system, and could influence the initial choice of material.…”

In Vitro Laser Ablation of Natural Marine Biofilms

“…After vortexing for 3 to 5 min to disperse the clumps (samples were observed under a microscope for the clump dispersion), subsamples were plated with ZoBell marine agar plates to estimate TVC. For the remaining sample, a hemocytometer was used to determine diatom density and species composition (13). Sixteen fields were counted for each sample.…”

Sunlight-enhanced calcareous deposition on cathodic stainless steel in natural seawater

“…Although larger numbers of diatoms were associated with the nighttime deposit rather than with the light-enhanced daytime deposit (Table 3), contrary to what might be expected, it must be taken into account that photosynthetic activity and the promotion of calcification may be controlled by the physiology of the algae rather than algal cell numbers (eg Abramovitch-Gottlib et al 2005). Also, calcium (Geesey et al 2000) and alkalinity (Nandakumar et al 2003) can favor the physiology of certain species of diatoms. Indeed, the dominant presence of Amphora spp.…”