Spatial analysis of water quality parameters in Hilo Bay, Hawai'i, using a combination of interpolated surfaces and hot spot analysis

Spatially-explicit water quality responses to freshwater discharge in a tropical estuary, Hilo Bay, Hawai‘i

“…Further evidence of surface-water discharge exiting the western half of the bay can be seen in a spatially interpolated rendering of water quality sampling from October 16, 2009 (Fig. 8), derived following the interpolation of Badlowski et al (2021). The date is one of moderately low ow (Fig.…”

“…However, this demonstrates why a spatially explicit analysis is important. In a previous analysis of spatially explicit samples, it was shown that signi cantly high measurements of turbidity and chlorophyll a were spatially offset (Badlowski et al 2021). A plume of elevated turbidity exiting the Wailuku River displaced elevated chlorophyll a concentrations and presumably pushed phytoplankton toward the breakwater.…”

“…The concept of spatially organizing an estuary is what sets this study apart from other studies, most of which employ point-speci c spot sampling (see Wiegner et al 2013 for example), and therefore, cannot examine how estuarine water quality is spatially organized. Other studies that have employed the high-density sampling methodology of Madden and Day (1992) have observed spatial patterns in estuarine water quality (Badlowski et al 2021), which led to the design of the current study. In Hilo Bay, a plume of shallow surface-water discharge in high-ow conditions is observed exiting the western half of the bay from the Wailuku River, particularly in the form of turbidity, whereas that same plume is largely absent from the eastern half of the bay (Fig.…”

“…High-density water quality measurements of salinity, turbidity, and chlorophyll a distributed at about every 40 m were collected using a Data ow system (Madden and Day 1992) as described in Badlowski et al (2021) on 19 sample dates between October 31, 2008 and January 21, 2011. Despite the age of the sample, the data are still relevant in distinguishing the effects of freshwater discharge on tropical estuary water quality in Hilo Bay.…”

“…The two rivers out ow on opposite sides of Hilo Bay, and establish a surface-water dominant half and groundwater dominant half of the bay. The groundwater dominant half of the bay is encircled by a breakwater, which introduces stark water quality contrasts on either side of the breakwater (Badlowski et al 2021). These various in uences of water quality in Hilo Bay are assessed here using a spatially explicit sampling method of many hundreds of water quality samples in the surface-water dominant half, groundwater dominant half, and at various locations around the breakwater.…”