Influences of N-Fixing and Non-N-Fixing Vegetation and Invasive Fish on Water Chemistry of Hawaiian Anchialine Ponds
Dudley BD, MacKenzie RA, Sakihara TS, Dulaiova H, Waters CA, Hughes RF, 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
Abstract: 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 nonnitrogen ( 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.
- Type
- Journal Article
- Authors
- Dudley, B.; MacKenzie, R.; Sakihara, T.; Dulaiova, H.; Waters, C.; Hughes, R.; Ostertag, R.
- Units
- KAHO
- Keywords
- anchialine pool, DIN, groundwater, Hawaii, nitrogen fixing, nutrient, poeciliid fish, Prosopis pallida, TDN, Thespesia populnea, water quality, watershed