Macroalgae and phytoplankton as indicators of ... - Naturstyrelsen

More documents

Recommendations

Info

In contrast to the other algal variables, the fraction of opportunists showed the strongest response to changing TN levels at low salinities (Figure 3.8F). Figure 3.8 Total algal cover (A), cumulated algal cover (B), cumulated cover of late-successionals (C), and number of latesuccessional algal species (D) in relation to concentrations of total nitrogen. Left panels show transformed (Tr.) data whereas right panels show backtransformed data. Algal variables are modelled for a water depth of 7 m and it is indicated which salinity range data represent. Regression lines describing empirical relationships between algal variables and TN-levels are shown for 3 salinities. The figure continues on the next page. 42
Figure 3.8 continued Cumulated cover of opportunists (E), and fraction of opportunists (F) in relation to concentrations of total nitrogen. Left panels show transformed (Tr.) data whereas right panels show backtransformed data. Algal variables are modelled for a water depth of 7 m and it is indicated which salinity range data represent. Regression lines describing empirical relationships between algal variables and TN-levels are shown for 3 salinities. 3.4.4 The "Spanish Index" tested on Danish macroalgal data A prerequisite for the "Spanish index" is that it reflects negative antropogenic influence on the marine environment. As it appears in the previous section, the cover of late-successional species, the fraction of opportunists as well as the number of late-successional species were all related to concentrations of total nitrogen (Table 3.9, Figures. 3.8B, E and F). The criterion for including these variables in the index was thus fulfilled for Danish coastal areas. The "Spanish index" operates with just two depth intervals. We found, not surprisingly, that each of the three components were depth dependent (Table 3.5) and showed marked changes with depth (Figure 3.6). Hard substrate in Danish waters is made up of boulders and stones nearly everywhere with changing depth distribution from site to site. Moreover, hard bottom is generally found on deeper waters in open and less polluted waters compared to sheltered fjords. This depth dependence and distribution pattern of hard substrate are not compatible with a scoring system with just two depth ranges. Rather, the depth dependence of the algal components must be better integrated in the scoring system. We also found that the level of algal components in the index varied markedly between areas (Table 3.5) and that salinity was an important variable affecting the algae (Table 3.9, Figure 3.7). The salinity will then have a strong influence in the index scores. 43
Page 1 and 2: National Environmental Research Ins
Page 3 and 4: National Environmental Research Ins
Page 5 and 6: Contents Summary 5 Sammenfatning 6
Page 7 and 8: Summary During the implementation o
Page 9 and 10: 1 Introduction This report is part
Page 11 and 12: Figure 2.1 Long-term trends in nitr
Page 13 and 14: Figure 2.2 Surface TN versus salini
Page 15 and 16: 2.2.2 Nitrogen input-TN relationshi
Page 17 and 18: Flensborg Fjord on the ranked scale
Page 19 and 20: 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: 3.4.3 Algal variables in relation t
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 and 72: 5 Conclusions and recommendations R
Page 73 and 74: 6 References Andersen, J., Markager
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
show all

Macroalgae and phytoplankton as indicators of ... - Naturstyrelsen

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?