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7.0 Appendix................................................................................................................... 102 |
vii |
List of Figures |
Figure 1. Seagrass species occurring in Florida.................................................................. 9 |
Figure 2. Study area located in North Biscayne Bay on the southeast coast of Florida. .. 17 |
Figure 3. Map of the Port of Miami sample location........................................................ 18 |
Figure 4. Location of the SFWMD and NOAA monitoring sites..................................... 28 |
Figure 5. Mean annual seagrass and algae frequency of occurrence................................ 34 |
Figures 6A-C. Mean seasonal seagrass species cover-densities....................................... 36 |
Figure 7. Mean seasonal average seagrass canopy height.. ............................................. 37 |
Figure 8. Mean annual seagrass species cover-densities. ................................................. 39 |
Figure 9. Mean annual seagrass species canopy heights. ................................................. 39 |
Figure 10. Mean annual average seagrass canopy height ................................................. 40 |
Figure 11. Mean annual algae group cover-densities ....................................................... 40 |
Figures 12A-E. Annual FIAN mean environmental and physical conditions.................. 45 |
Figures 13A-E. Seasonal FIAN mean environmental and physical conditions................ 47 |
Figures 14A-C. Annual FIAN and SFWMD environmental conditions .......................... 55 |
Figures 15A-B. NOAA Weather Graphs.......................................................................... 57 |
viii |
List of Tables |
Table 1. Measurement and method for biotic and environmental and physical |
measurements used to characterize sampling locations in FIAN. .................................... 26 |
Table 2. Environmental and physical measurements from all agencies used in this study |
to characterize the POM sampling location. ..................................................................... 29 |
Table 3. FIAN Percentage of each vegetation genera present at all the sample sites and |
quadrats over the study period. ......................................................................................... 32 |
Table 4. FIAN Frequency of sites within the POM basin with mixed or monospecific |
seagrass beds and no grass present ................................................................................... 33 |
Table 5. Mann-Whitney U test of significance for seasonal differences of canopy height, |
average canopy height and vegetation cover-density . ..................................................... 35 |
Table 6. Kruskal Wallis test of differences in seagrass canopy height and vegetation |
cover-densities among years. ............................................................................................ 38 |
Table 7. Kruskal Wallis test on average seagrass canopy height and vegetation coverdensities between collection sites (1-30) within the Port of Miami basin. ....................... 41 |
Table 8. Seagrass cover-densities descriptives by site (1-30) and location type within the |
Port of Miami basin. ......................................................................................................... 42 |
Table 9. General Linear Model of environmental and physical variables in FIAN data by |
Year*Season. .................................................................................................................... 44 |
Table 10. One-way ANOVA results for spatial effects of environmental and physical |
Measurements among the 30 sample sites within the POM basin.................................... 51 |
Table 11. SFWMD average monthly water quality parameters. ..................................... 54 |
Table 12. Models 1A-D. Multiple Regression models for Seagrass occurrence and |
environmental variables.................................................................................................... 59 |
Table 13. Models 2-4 A -D. Multiple Enter-wise Regression models for individual |
seagrass cover-densities and environmental and physical measurements........................ 62 |
Table 14. Models 5A-D. Multiple Enter-wise Regression Models for Average Seagrass |
Canopy height and environmental and physical measurements..…..….………………...66 |
ix |
List of Appendices |
Appendix 1. Temporal Vegetation Descriptives............................................................. 102 |
Appendix 2. Temporal Canopy Height Descriptives...................................................... 103 |
Appendix 3. Temporal Environmental and Physical Descriptives. ................................ 104 |
Appendix 4. Spatial Vegetation Descriptives. ............................................................... 105 |
Appendix 5. Spatial Canopy Height Descriptives. ........................................................ 106 |
Appendix 6. Spatial Environmental and Physical Descriptives..................................... 107 |
1 |
1.0 Introduction |
Coastal communities have some of the densest human populations and are more |
vulnerable to environmental impacts. South Florida is home to a rising coastal |
population and has many valuable natural resources, including the seagrass communities. |
Human population expansion and the increasing anthropogenic inputs to the coastal |
waters are perceived as the dominant cause of the world-wide decline in seagrasses |
habitat (Short and Wyllie-Echeverria 1996). Major epicenters for seagrass loss are |
adjacent to areas of dense human populations and most of the declines appear to be |
related to human activities, many of which impact the light available for plant |
photosynthesis (Kemp 2000). The habitat that remains reflects the influence of the |
surrounding urban environment. |
Anthropogenic seagrass losses have been attributed to many direct and indirect |
causes. Most such losses result from human activities that increase inputs of nutrients |
and sediment into the coastal zone (Short and Wyllie-Echeverria 1996), reducing water |
clarity. Coastal development involving dredge-and-fill activities can impact seagrass |
meadows in two ways: through direct physical impact (e.g. removing the plants and the |
underlying sediments or by killing the plants by covering them with a thick layer of fill |
material) or through indirect effect (e.g. reduced water clarity by increased turbidity) |
(Lewis 1977; Janicki et al. 1995; Yates et al. 2011). Despite the recognition of seagrass |
beds as some of the world’s most productive and valuable ecosystems, anthropogenic |
losses of these habitats continue at an alarming rate (Short and Wyllie-Echeverria 1996). |
Over the past century, anthropogenic and natural disturbances have dramatically |
influenced the coasts in Miami, Florida. The amount of seagrass habitat that remains is |
dependent on stable environmental and physical conditions for growth; however, with |
construction activities for human expansion in the Port of Miami (POM) and the threat of |
extreme weather events, the potential for seagrass habitat loss exists. |
2 |
1.1 Seagrass Natural History |
Seagrasses are a mixed group of clonal flowering plants which grow submerged |
in shallow marine and estuarine environments, exhibiting a low taxonomic diversity with |
about 60 species worldwide (Green and Short 2003; Peterson and Fourqurean 2001). |
Seagrasses are not true grasses and are more closely related to lilies but they appear |
grass-like with shoots of three to five leaf blades attached to a horizontal stem and thick |
roots and rhizomes that allow them to anchor themselves into the bottom sediment |
(McKenzie 2008). They come in a variety of shapes and sizes depending on species, but |
both the leaves and stems of seagrasses contain air channels for transport of water, food |
and absorption of gases (McKenzie 2008). The strong root structure allows seagrasses to |
withstand strong currents and waves, especially during storm events (GMP 2004). The |
structure of these plants, as well as the height of the canopy and the extent of the |
meadow, is influenced by a number of ecological factors (Björk et al. 2008). |
Seagrasses can reproduce both sexually and asexually (Ewanchuk and Williams, |
1996). Most seagrass stands begin as seedlings that spread through vegetative rhizome |
expansion and new shoot production until they form clonal patches, beds and, eventually, |
meadows (Björk et al. 2008). The life span of seagrass modules is scaled to their size, |
with small species having short leaf life spans and larger species having longer leaf life |
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