Identifying nitrogen sources to thermal tide pools in Kapoho, Hawai'i, U.S.A, using a multi-stable isotope approach

Abstract

Nitrogen (N) enrichment often results in coastal eutrophication, even in remote areas like Hawai'i. Therefore, determining N sources to coastal waters is important for their management. This study identified N sources to tide pools in Kapoho, Hawai'i, and determined their relative importance using three stable isotopes (δ(15)N, δ(18)O, δ(11)B). Surface waters and macroalgal tissues were collected along 100-m onshore-offshore transects in areas of high groundwater input for three months at low tide. Water samples from possible N sources were also collected. Mixing model output, along with macroalgal δ(15)N values, indicated that agriculture soil (34%) was the largest anthropogenic N source followed by sewage (27%). These findings suggest that more effective fertilizer application techniques and upgrading sewage treatment systems can minimize N leaching into groundwater. Overall, our multi-stable isotope approach for identifying N sources was successful and may be useful in other coastal waters.

Symbiont type and environmental factors affect transcriptome‐wide gene expression in the coral Montipora capitata

“…In contrast, Waiʻōpae on the Eastern side received higher rainfall and groundwater influx and was defined by its complex underwater topography with partially submerged tide pools of different size and connectivity to the open ocean. Waiʻōpae was therefore subject to much higher fluctuations in temperature and salinity (Wiegner et al, ) than Kīholo, necessitating different short‐ and long‐term physiological responses. The magnitude of gene expression differences between sites was comparable to those in a similar study, which reported about 3,000 DEGs between two sites (Barfield et al, ) in Australian A. millepora .…”

“…Waiʻōpae, while on an open coastline, was composed of numerous permanently and temporarily submerged basaltic tidepools, ranging in size and connectivity at low tide ( c. 1 m 3 to 2,500 m 3 , 0.25–3 m depth). Such complex underwater topography at Waiʻōpae, along with high rainfall and groundwater discharge, created high variability in temperature and salinity (Wiegner, Mokiao‐Lee, & Johnson, ).…”

Coral Skeletons Record Increasing Agriculture‐Related Groundwater Nitrogen Inputs to a South Pacific Reef Over the Past Century

“…• Data Set S1 Lapointe et al, 1999;Lapointe & Clark, 1992;Wiegner et al, 2016). However, there is limited data available describing temporal site-specific patterns of groundwater nutrient discharge and how these may have changed as a result of anthropogenic activity.…”

“…In many Pacific Island nations, rapid tourist and agricultural development, since the 1960s, has led to concerns over the contamination of coastal aquifers with anthropogenic nutrients (Knee & Paytan, ; Lapointe et al, ; Lapointe & Clark, ; Wiegner et al, ). However, there is limited data available describing temporal site‐specific patterns of groundwater nutrient discharge and how these may have changed as a result of anthropogenic activity.…”

Phenotypic diversity within two toxic dinoflagellate genera: environmental and transcriptomic studies of species diversity in Alexandrium and Gambierdiscus

“…Nutrient concentrations also increase closer to shore. In another study of surface waters near these sampling sites, total dissolved nitrogen (TDN) ranged from 18 to 11 μmol L −1 from 0 to 100m from shore (Wiegner, Mokiao-Lee, & Johnson, 2016). Sites further from shore also have higher coral cover though corals are present near all sites.…”