Macroalgae and phytoplankton as indicators of ... - Naturstyrelsen

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tween reference conditions and good-moderate boundaries for eelgrass depth limits and the corresponding values for chla. Precision of the two different chla indicators 'summer mean' (used in the Baltic GIG) and '90-percentile' (used in the North East Atlantic GIG) was evaluated using theoretical parametric distributions and empirical distributions based on monitoring data (summer chla values (May- September) over a 6-year period (2001-2006) from 4 stations representing a gradient from open water to eutrophic estuary). The 90-percentile was clearly substantially more uncertain that the mean or median indicators, particularly for small sample sizes but also for large sample sizes (factor of 3-5). The 90-percentile as an indicator is useful only if it can be documented that this indicator relates more strongly to nutrient status than the mean, i.e. that nutrient enrichment should affect phytoplankton bloom concentrations more than the overall chla concentration. So far, this has not been documented. We recommend that the decision to use the 90-percentile as indicator for phytoplankton biomass in the North East Atlantic GIG is revised to a mean indicator. This will also allow for comparison with results from the Baltic GIG. 70
6 References Andersen, J., Markager, S.. & Ærtebjerg G. (red.) 2004: Tekniske anvisninger for marin overvågning. National Environmental Research Institute, Denmark. http://www.dmu.dk/Overvaagning/Fagdatacentre/Det+Marine+Fagd atacenter/Tekniske+anvisninger+NOVANA+2004-2009 / Borum, J. 1985: Development of epiphytic communities on eelgrass (Zostera marina) along a nutrient gradient in a Danish estuary. - Marine Biology 87: 211-218. Carstensen, J. 2007: Statistical principles for ecological status classification of Water Framework Directive monitoring data. - Marine Pollution Bulletin 55: 3-15. Carstensen, J., Conley, D.J. & Müller-Karulis, B. 2003: Spatial and temporal resolution of carbon fluxes in a shallow coastal ecosystem, the Kattegat. - Marine Ecology Progress Series 252: 35-50. Carstensen, J., Conley, D.J. & Henriksen, P. 2004: Frequency, composition and causes of summer phytoplankton blooms in a shallow coastal ecosystem, the Kattegat. - Limnology and Oceanography 49: 191-201. Carstensen, J., Henriksen, P. & Heiskanen, A.-S. 2007: Summer algal blooms in shallow estuaries: Definition, mechanisms and link to eutrophication. - Limnology and Oceanography 52: 370-384. Carstensen, J., Krause-Jensen, D., Dahl. K. & Middelboe, A.L. 2005: Development of macroalgal indicators of water quality. - In: Petersen, J.K., Hansen, O.S., Henriksen, P., Carstensen, J., Krause-Jensen, D., Dahl, K., Josefson, A.B., Hansen, J.L.S., Middelboe, A.L. & Andersen, J.H; Scientific and technical background for intercalibration of Danish coastal waters. National Environmental Research Institute, Denmark. - NERI Technical Report No. 563, Ch. 3, pp. 27-58. http://technical-reports.dmu.dk Cleveland, W.S. 1979: Robust locally weighted regression and smooting scatterplots. - Journal of the American Statistical Association 74: 829-836. Conley, D.J., Carstensen, J., Ærtebjerg, G., Christensen, P.B., Dalsgaard, T., Hansen, J.L.S. & Josefson, A. 2007: Long-term changes and impacts of hypoxia in Danish coastal waters. - Ecological Applications 17(5) Supplement: S165-S184. Dahl, K. & Carstensen, J. 2008: Tools to access conservation status on open water reefs in Nature-2000 areas. National Environmental Research Institute, University of Aarhus. 25 pp. - NERI Technical Report No. 663. http://www.dmu.dk/Pub/FR663.pdf Duarte, C.M. 1991: Seagrass depth limits. - Aquatic Botany 40: 363-377. 71
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National Environmental Research Ins
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National Environmental Research Ins
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Contents Summary 5 Sammenfatning 6
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Summary During the implementation o
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1 Introduction This report is part
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Figure 2.1 Long-term trends in nitr
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Figure 2.2 Surface TN versus salini
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2.2.2 Nitrogen input-TN relationshi
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Flensborg Fjord on the ranked scale
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Table 2.4 Suggested reference condi
Page 21 and 22: the gradient. These responses have
Page 23 and 24: Table 3.1 Overview of sampling area
Page 25 and 26: We assumed that mean values from th
Page 27 and 28: and 2005), averaged over the months
Page 29 and 30: The second component of the Spanish
Page 31 and 32: The variance of a macroalgae indica
Page 33 and 34: The levels of mean cumulated algal
Page 35 and 36: Figur 3.5 continued Modelled mean l
Page 37 and 38: while the fraction of opportunists
Page 39 and 40: 3.4.2 Physico-chemical variables Ph
Page 41 and 42: Figure 3.7 continued Mean modelled
Page 43 and 44: 3.4.3 Algal variables in relation t
Page 45 and 46: Figure 3.8 continued Cumulated cove
Page 47 and 48: inputs (Figures 3.9 and 3.10) where
Page 49 and 50: A Total algal cover (%) 100 95 90 8
Page 51 and 52: A 100 B 140 Total algal cover (%) 8
Page 53 and 54: A response to changes in nutrient c
Page 55 and 56: In its present form the Spanish ind
Page 57 and 58: 3.6 Conclusions • All algal varia
Page 59 and 60: gime shift after changing the sluic
Page 61 and 62: Figure 4.3 Estimated site-specific
Page 63 and 64: from Randers Fjord and Odense Fjord
Page 65 and 66: moderate boundaries. Reference dept
Page 67 and 68: 4.3 Evaluation of the precision of
Page 69 and 70: The 90-percentile was clearly subst
Page 71: 5 Conclusions and recommendations R
Page 75: Nielsen, S.L., Sand-Jensen, K., Bor
Page 78 and 79: 76 Appendix 1. Reference levels and
Page 84 and 85: Appendix 7. Modelled mean levels of
Page 86 and 87: Appendix 9. Modelled mean levels of
Page 88 and 89: Appendix 11. Modelled mean levels o
Page 90 and 91: Appendix 13. Results of power analy
Page 92 and 93: Appendix 18. Results of power analy
Page 94 and 95: NERI Technical Reports NERI’s web
Page 96: of Danish coastal waters 683 Macroa
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