State of the Bay Report 2011-Final.pdf - Anchor Environmental

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State of Saldanha Bay & Langebaan Lagoon 2011 Intertidal invertebrates The site at the Iron Ore Terminal (IO) is sheltered to semi-exposed with a very steep slope resulting in a very narrow total shore width (distance from low water to high water mark). The rocky surface of this site comprises of medium-sized broken boulders that are piled up to support a side arm of the iron ore terminal (Figure 8.3), which encircles a small area that was previously used for aquaculture purposes. The semi-exposed site Lynch Point (L) has a relatively smooth surface with occasionally deep crevices running across (Figure 8.3). North Bay (NB) is semiexposed to exposed with a relatively flat high and mid shore (Figure 8.3). The low shore consists of large unmovable square boulders separated by channels. The rocky intertidal site on Marcus Island (M) is very flat and openly exposed to the swell (Figure 8.3). 8.2.2 Methods The unique physical environment of the rocky intertidal alternately exposes it to air and submerges it under water, creating a steep vertical environmental gradient for the biota that inhabits these shores. Rocky shores can thus be partitioned into different zones according to shore height level whereby each zone is distinguishable by their different biological communities (Menge & Branch 2001). At each study site, the rocky intertidal was divided into three shore height zones: the high, mid and low shore. In each of these zones, six 100°x°50-cm quadrats were randomly placed on the shore and the percentage cover of all visible species recorded as primary (occurring on the rock) and secondary (occurring on other benthic fauna or flora) cover, and individual mobile organisms counted to calculate densities within the quadrat area (0.5m 2 ). The quadrat was subdivided into smaller squares, to aid in the estimation of the percentage cover. Finally, the primary and secondary cover data for both mobile and sessile organisms were combined and down-scaled to 100%. This survey protocol is consistent with the previous survey protocols. A species list is provided in the Appendix. Sampling is non-destructive, i.e. the biota is not removed from the shore, and smaller infaunal species (e.g. polychaetes, amphipods, isopods) that live in the complex matrix of mussel beds or dense stands of algae are thus not recorded in this survey protocol. Additionally, some algae and invertebrates cannot be easily identified to generic or species level in the field and are thus recorded under a general heading only (e.g. crustose and articulate corallines, red turfs, sponge, colonial ascidian). For further analysis, intertidal species were categorized into ten functional groups: a) grazers, mostly limpet species, b) trappers, limpet species that specifically trap kelp fronds beneath their shells, c) filter-feeders, particularly sessile suspension feeders such as mussels and barnacles, d) mobile predators and scavengers, such as carnivorous whelks, e) anemones, f) crustose 2 and g) articulated coralline 3 algae, h) corticated 4 and i) ephemeral foliose 5 seaweeds and j) kelps. 2 Crustose (or encrusting) corallines - Crustose corallines are typically slow growing crusts of varying thickness that can occur on rock, shells, or other algae. 3 Articulated corallines - Articulated corallines are branching, small tree-like plants, which are attached to the substratum by crustose or calcified, root-like holdfasts. 4 Corticated algae - Algae that have secondarily formed outer cellular covering over part or all of an algal thallus. Usually relatively large and long-lived. 5 Ephemeral algae - Opportunistic algae with a short life cycle that are usually the first settlers on a rocky shore. 166 ANCHOR e n v i r o n m en t a l
State of Saldanha Bay & Langebaan Lagoon 2011 Intertidal invertebrates 8.2.3 Data Analysis The similarities or dissimilarities among the quadrats from the eight different study sites are analyzed with multivariate analyses techniques employing the software package PRIMER 6. These methods are useful for a graphical presentation of the results obtained from the typically large data sets collected during ecological sampling. The principle aim of these techniques is to discern the most conspicuous patterns in the community data. Comparisons between intertidal communities are based on the extent to which they share particular species at similar levels of occurrence. Patterns in the data are represented graphically through hierarchical clustering (dendrogram) and multi-dimensional scaling (MDS) ordination techniques. The former produces a dendrogram in which samples with the greatest similarity are fused into groups, and these are successively grouped into clusters as the similarity criteria defining the groups are gradually reduced. MDS techniques compliment hierarchical clustering methods by more accurately ‘mapping’ the sample groupings two-dimensionally in such a way that the distances between samples represent their relative similarities or dissimilarities. Whether (a priori defined) groups of samples (e.g. sites, treatments, years) are statistically different is analysed by means of PERMANOVA. PERMANOVA is a routine for testing the simultaneous response of one or more variables to one or more factors in an analysis of variance (ANOVA) experimental design on the basis of any resemblance measure, using permutation methods (Anderson et al. 2008). In essence, the routine performs a partitioning of the total sum of squares according to the specified experimental design, including appropriate treatment of factors that are fixed or random, crossed or nested, and all interaction terms. A distance-based pseudo-F statistic is calculated in a fashion that is analogue to the construction of the F statistic for multi-factorial ANOVA models. P-values are subsequently obtained using an appropriate permutation procedure for each term. Following the main overall test, pair-wise comparisons are conducted. Significance level for the PERMANOVA routine is p
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Mussels Oysters Abalone Scallops Re
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Cadmium (mg/kg) Lead(mg/kg) Mercury
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Beach Width (m) State of Saldanha B
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Copper (mg/kg) Copper (mg/kg) Coppe
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