TABLE 1.

Habitats and broader categories included in UniFrac P analyses^a

Category	Habitat	No. of sequences
		Chitinase genes	16S rRNA genes
Salinity	Freshwater	20	30
	Estuarine	14	34
	Marine	166	310
	Hypersaline	19	30
Latitude	Tropic climate zone (23.5°N to 23.5°S)	112	137
	Nontropic climate zone (>23.5°N, >23.5°S)	111	166
Coastal/open ocean	Coastal	46	147
	Open ocean	120	156
Geographic	Caribbean Sea	20	50
locationb	Galapagos Islands	61	88
	Indian Ocean	28	95
	North American East Coast	16	54
	Sargasso Sea	86	44

^aWith the exception of the category for geographic location, only coastal and open ocean samples were included to represent marine samples in the analyses. The number of sequences included in each habitat is listed for the chitinase and 16S rRNA gene. These habitats were based only on planktonic samples (filter size, <0.8 μm) of group A chitinases. Habitats with fewer than 10 chitinase genes were excluded from further analyses to avoid spurious results. The habitats were further grouped into categories. Samples from a mangrove environment were grouped together with estuarine samples since satellite pictures from the Google Earth software tool (version 4.3.7204.0836 [beta]) show freshwater intrusion at this site. To avoid the influence of special marine habitats, such as reef samples, only coastal and open ocean samples were included in the respective habitats for salinity, latitude, and proximity to the coastline. However, we included sequences from all marine planktonic samples in habitats within the geographic location category, since too few sequences remained for the single categories.

^bOnly sites with at least 10 chitinase sequences were included.