Victorian Subtidal Reef Monitoring Program - Parks Victoria

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Parks Victoria Technical Series No. 28PPB Sanctuaries Subtidal Reef Monitoring2.2.5 Method 4 – MacrocystisIn addition to macroalgal cover, the density of Macrocystis angustifolia plants is estimated.While swimming along the 200 m transect line, a diver counts all observable plants within5 m either side of the line, for each 10 m section of the transect (giving counts for 100 m 2sections of the transect).Table 2.3 Invertebrates and cryptic fish surveyed in northern Port Phillip Bay using Method 2.Method 2Mollusca Echinodermata PolychaetaPlagusia chabrus Tosia australis Sabella spallanzaniHaliotis rubraTosia magnificaDiodora lineata Petricia vernicina Cryptic FishDicathais orbita Patiriella exigua Aetapcus maculatusPleuroploca australasia Patiriella calcar Vincentia conspersaCeratosoma brevicaudatum Patiriella brevispina Pempheris multiradiataOstrea angasi Coscinasterias muricata Bovichtus angustifronsAsterias amurensisParablennius tasmanianusCrustacea Uniophora granifera Norfolkia clarkeiStrigopagurus strigimanus Amblypneustes sp. Heteroclinus perspicillatusPagurid unidentified Heliocidaris erythrogramma Nesogobius sp.Nectocarcinus tuberculatusBrachaluteres jacksonianusTable 2.4 Macroalgae surveyed in northern Port Phillip Bay using Method 3.Method 3Chlorophyta (green) Phaeophyta (brown) Rhodophyta (red algae)Ulva spp Leathesia difformis Haliptilon roseumCladophora prolifera Splachnidium rugosum Encrusting corallinesCladophora spp Dictyota dichotoma Gigartina sp.Caulerpa remotifolia Dilophus marginatus Callophyllis rangiferinaCaulerpa longifolia Lobospira bicuspidata Plocamium angustumCaulerpa brownii Distromium flabellatum Dictymenia harveyanaCaulerpa flexilis Zonaria turneriana Laurencia filiformisCaulerpa geminata Colpomenia peregrina Laurencia tumidaCaulerpa simpliciusculaEcklonia radiataCodium spp Caulocystis cephalornithos Sessile InvertebratesFilamentous greens Acrocarpia paniculata Other spongesCystophora moniliformis Plesiastrea versiporaCystophora retroflexaAmathia sp.Cystophora subfarcinata Unidentified colonial ascidianSargassum linearifolium Erythropodium hicksoniiSargassum spinuligerumSargassum spp10
Parks Victoria Technical Series No. 28PPB Sanctuaries Subtidal Reef Monitoring2.3 Data AnalysisTo identify changes and trends within marine protected areas, sites from inside each MPAwill be compared to paired reference sites outside each MPA. For the first survey, data fromall sites is compared together. This allows an assessment of biota at each site to be placedin a bioregional context. Descriptions of the biota and community structure at each site arealso provided.2.3.1 Community StructureCommunity structure is a function of both the species present and the abundance of eachspecies. The community structure between pairs of samples was compared using the Bray-Curtis dissimilarity coefficient. This index compares the abundance of each species betweentwo samples to give a single value of the difference between the samples, expressed as apercentage (Faith et al. 1987; Clarke 1993).Prior to analysis, the data were log transformed to weight down the influence of highlyabundant species in describing community structure, giving a more even weighting betweenabundant and rarer species (following abundance transformations by Sweatman et al. 2000).The Bray-Curtis dissimilarity index was calculated for all possible combinations of sites. Thisresulted in a matrix of pair-wise comparisons known as a dissimilarity matrix. Thedissimilarity matrix is also termed a distance matrix as it effectively represents distancesbetween samples in hyper-dimensional space. The dissimilarity matrix was used for allanalyses of community structure in this study.2.3.2 Depiction of Community DifferencesThe hyper-dimensional information in the dissimilarity matrix was simplified and depictedusing non-metric multidimensional scaling (MDS; Clarke 1993). This ordination method findsthe representation in fewer dimensions that best depicts the actual patterns in the hyperdimensionaldata (i.e. reduces the number of dimensions while depicting the salientrelationships between the samples). The MDS results were then depicted graphically to showdifferences between the replicates at each location. The distance between points on the MDSplot is representative of the relative difference in community structure.Kruskall stress is an indicator statistic calculated during the ordination process and indicatesthe degree of disparity between the reduced dimensional data set and the original hyperdimensionaldata set. A guide to interpreting the Kruskall stress indicator is given by Clarke(1993): (< 0.1) a good ordination with no real risk of drawing false inferences; (< 0.2) canlead to a usable picture, although for values at the upper end of this range there is potentialto mislead; and (> 0.2) likely to yield plots which can be dangerous to interpret. Theseguidelines are simplistic and increasing stress is correlated with increasing numbers ofsamples. Where high stress was encountered with a two-dimensional data set, threedimensionalsolutions were sought to ensure an adequate representation of the higherdimensionalpatterns.11
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