Title: Influences of N-fixing and non-N-fixing vegetation and invasive fish on water chemistry of Hawaiian anchialine ponds
Author: Dudley, B. D.; MacKenzie, Richard; Sakihara, T. S.; Dulaiova, H.; Waters, C. A.; Hughes, Flint; Ostertag, R.;
Source: Pacific Science. 68(4): 509-523
Publication Series: Scientific Journal (JRNL)
Description: In coastal waters, it remains unclear how terrestrial invasive species might alter nutrient availability and thus affect bottom-up control of primary production. Anchialine ponds are tidal- and groundwater-fed coastal water bodies without surface connections that provide convenient model systems in which to examine terrestrial to aquatic nutrient flow. To investigate how N-fixing and non-N-fixing terrestrial vegetation and invasive consumers affect water quality, we compared dissolved nutrient concentrations and physicochemical parameters among Hawaiian anchialine ponds surrounded by: (1) the non-nitrogen ( N)-fixing tree Thespesia populnea (milo), (2) the exotic N-fixing tree Prosopis pallida ( kiawe), (3) no tree cover, and (4) no tree cover but containing populations of invasive poeciliid fish. Average (±1 SE) concentration of dissolved inorganic nitrogen (DIN) across all ponds (51.15 μM ± 3.1; n = 17) was high, but there was no discernible pattern among pond types. Model results suggest that leaf litter breakdown from the exotic N-fixing tree contributed <0.02% of total dissolved nitrogen (TDN) in the water column at high tide. However, additions of phosphorus (P), especially from litter of non-N-fixing T. populnea, resulted in ratios of DIN to soluble reactive phosphorus (SRP) that varied between 4.5:1 and 35:1 across pond types. Our study suggests that: (1) DIN concentrations were more dependent on watershed-scale N inputs than local tree cover or the presence of poeciliids, (2) low water residence times in these ponds reduce effects of local biota on water nutrient chemistry, and (3) P from anthropogenic inputs and /or biota cause alterations to DIN:SRP ratios in anchialine pond water that may potentially alter primary production rates in these coastal ecosystems.
Keywords: nitrogen, anchialine ponds, kiawe, poeciliids, water quality
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Dudley, B. D.; MacKenzie, R. A.; Sakihara, T. S.; Dulaiova, H.; Waters, C. A.; Hughes, R. F.; Ostertag, R. 2014. Influences of N-fixing and non-N-fixing vegetation and invasive fish on water chemistry of Hawaiian anchialine ponds. Pacific Science. 68(4): 509-523.
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