Janet M. Carey

Development of the primary bacterial microfouling layer on antifouling and fouling release coatings in temperate and tropical environments in Eastern Australia

The role played by bacteria during the pioneering stages of colonisation on marine coatings was investigated over three distinct seasons in both tropical and temperate environments. Novel methods were developed to facilitate the study of the adhered bacterial population on the test coatings in their native, hydrated state. The approach eliminated destructive sample preparation techniques, including sample dehydration and/or removal from the substratum surface prior to analysis. Bacterial colonisation during initial biofilm formation was evaluated on two antifouling paints, Intersmooth 360® and Super Yacht 800®, and a fouling release coating, Intersleek 700®. Bacterial colonisation was quantified on all three coating surfaces. Intersleek 700 displayed the quickest colonisation by bacteria, resulting in major modification of the substratum surface within 2–4 days following immersion in the ocean. Whilst fouling accumulated more quickly on Intersleek 700, by 16 days all three coatings were fouled significantly. Bacterial fouling was correlated to both location and season, with fouling occurring at a more rapid rate at the Cairns location, as well as during the summer months, when higher water temperatures were recorded. Successful colonisation of all coatings by bacteria soon after immersion modifies the characteristics of the surfaces at the hull/water interface, and subsequent settlement by higher biofouling organisms must be moderated by these modified surfaces.

Linguistic Uncertainty in Qualitative Risk Analysis and How to Minimize It

Most risk assessments assume uncertainty may be decomposed into variability and incertitude. Language is often overlooked as a source of uncertainty, but linguistic uncertainty may be pervasive in workshops, committees, and other face‐to‐face language‐based settings where it can result in misunderstanding and arbitrary disagreement. Here we present examples of linguistic uncertainty drawn from qualitative risk analysis undertaken in stakeholder workshops and describe how the uncertainties were treated. We used a process of iterative re‐assessment of likelihoods and consequences, interspersed with facilitated discussion, to assist in the reduction of language‐based uncertainty. The effects of this process were evident as changes in the level of agreement among groups of assessors in the ranking of hazards.

The Variability of Estimates of Variance, and Its Effect on Power Analysis in Monitoring Design

Power analysis can be a valuable aid in the design of monitoringprograms. It requires an estimate of variance, which may come from a pilot study or an existing study in a similar habitat. For marine benthic infauna, natural variation in abundances canbe considerable, raising the question of reliability of varianceestimates. We used two existing monitoring programs to generatemultiple estimates of variance. These estimates were found to differ from nominated best estimates by 50% or more in 43% of cases, in turn leading to under or over-estimation of samplesize in the design of a notional monitoring program. The twostudies, from the same general area, using the same samplingmethods and spanning a similar time scale, gave estimatesvarying by more than an order of magnitude for 25% of taxa.We suggest that pilot studies for ecological monitoring programsof marine infauna should include at least two sampling times.

Long-term changes in macroalgal assemblages after increased sedimentation and turbidity in Western Port, Victoria, Australia

The long-term impacts of declining water quality from coastal development on macro-algal communities can be devastating, but are rarely known because of lack of baseline studies. This study examines the effect of increased sediment and reduced water quality over 35 years in an Australian temperate coastal embayment. The algal assemblage on Crawfish Rock in northern Western Port was surveyed in 1967–1971 and in 2002–2006. During the 1980s, water quality declined following large-scale seagrass loss. In 1971, the Rock had a rich algal flora with 138 recorded species, including 97 species of Rhodophyta. The biomass and cover of canopy and understorey species were measured at sites of strong and slight current on a depth gradient. In 1971, fucoid or laminarian canopy species were dominant from ;1–8 m depth, and an algal understorey extended from the intertidal zone to 12–13 m depth. In 2002–2006 the canopy species extended to only 3 m depth and the algal understorey to ;4 m depth, and 66% of the algal species had disappeared, although a few additional species were present. Persistent, sediment-tolerant species included several phaeophycean canopy species, some chlorophytes (Caulerpa spp.) and a few rhodophytes.

Compositing and Subsampling to Reduce Costs and Improve Power in Benthic Infaunal Monitoring Programs

Monitoring of soft-sediment infauna can be a useful tool in impact assessment, but sorting of specimens from sediments may be very time consuming and expensive. This can force a reduction in the intended sampling program, leading to low statistical power and increased uncertainty in decision making. We pooled field samples of marine infauna into composites, then exhaustively subsampled the composites to examine the statistical distribution of organisms in the subsamples. Abundances of organisms among subsamples were generally consistent with a random distribution, with deviations from randomness occurring more frequently for standard replicates than for subsamples. For the most abundant taxa, subsamples had much smaller variances than replicates, and in 76% of cases, the type of sample (i.e., subsample or replicate) had no effect on the mean abundance of organisms recorded. As our subsamples appeared generally unbiased, we then considered the cost and power for hypothetical monitoring programs using an MBACI analysis, and found substantial cost savings and increases in power to detect impact by using compositing and subsampling.

An Application of Qualitative Risk Assessment in Park Management

The identification and prioritisation of natural values and the potential threats to them is an essential part of the management of parks and reserves by Parks Victoria, which regularly explores alternative ways to undertake and improve the efficiency of this process. Here we describe an application of ecological risk assessment techniques for identifying and analysing risks to natural values in the mallee national parks of north-western Victoria. Utilizing a workshop setting and multiple assessors, hazards were identified with the aid of a hazard matrix. A modification of the risk analysis protocol from the Australian Standard for Risk Management, AS/NZS 4360, was used to facilitate assessment by multiple participants and to capture the full range of their judgements so as to best characterise threats to natural values. An iterative process provided opportunity to resolve uncertainty due to linguistic ambiguity and vagueness, and genuine differences of opinion that remained were explicitly represented in the final ranking of the hazards. A fault tree was then used to explore the ecological complexities behind one particular issue of concern in the mallee parks.