Geology topics

Ron A. Heintz

Publications and source records attributed to Ron A. Heintz.

4 recordsLinked to original sources

USGS2013

Seasonal persistence of marine-derived nutrients in south-central Alaskan salmon streams

Spawning salmon deliver annual pulses of marine-derived nutrients (MDN) to riverine ecosystems around the Pacific Rim, leading to increased growth and condition in aquatic and riparian biota. The influence of pulsed resources may last for extended periods of time when recipient food webs have effective storage mechanisms, yet few studies have tracked the seasonal persistence of MDN. With this as our goal, we sampled stream water chemistry and selected stream and riparian biota spring through fall at 18 stations (in six watersheds) that vary widely in spawner abundance and at nine stations (in three watersheds) where salmon runs were blocked by waterfalls. We then developed regression models that related dissolved nutrient concentrations and biochemical measures of MDN assimilation to localized spawner density across these 27 stations. Stream water ammonium-N and orthophosphate-P concentrations increased with spawner density during the summer salmon runs, but responses did not persist into the following fall. The effect of spawner density on δ 15 N in generalist macroinvertebrates and three independent MDN metrics (δ 15 N, δ 34 S, and ω3:ω6 fatty acids) in juvenile Dolly Varden (Salvelinus malma) was positive and similar during each season, indicating that MDN levels in biota increased with spawner abundance and were maintained for at least nine months after inputs. Delta 15 N in a riparian plant, horsetail (Equisetum fluviatile), and scraper macroinvertebrates did not vary with spawner density in any season, suggesting a lack of MDN assimilation by these lower trophic levels. Our results demonstrate the ready assimilation of MDN by generalist consumers and the persistence of this pulsed subsidy in these organisms through the winter and into the next growing season.

Alaska↗

USGS2012

Pacific salmon (Oncorhynchus spp.) runs and consumer fitness: growth and energy storage in stream-dwelling salmonids increase with salmon spawner density

We examined how marine-derived nutrients (MDN), in the form of spawning Pacific salmon, influenced the nutritional status and δ 15 N of stream-dwelling fishes. We sampled juvenile coho salmon ( Oncorhynchus kisutch ) and Dolly Varden ( Salvelinus malma ) during spring and fall from 11 south-central Alaskan streams that ranged widely in spawning salmon biomass (0.1–4.7 kg·m –2 ). Growth rate (as indexed by RNA–DNA ratios), energy density, and δ 15 N enrichment in spring-sampled fishes increased with spawner biomass, indicating the persistence of spawner effects more than 6 months after salmon spawning. Point estimates suggest that spawner effects on nutrition were substantially greater for coho salmon than Dolly Varden (268% and 175% greater for growth and energy, respectively), indicating that both species benefitted physiologically, but that juvenile coho salmon accrued more benefits than Dolly Varden. Although the data were less conclusive for fall- than spring-sampled fish, they do suggest spawner effects were also generally positive during fall, soon after salmon spawned. In a follow-up analysis where growth rate and energy density were modeled as a function of δ 15 N enrichment, results suggested that both increased with MDN assimilation, especially in juvenile coho salmon. Our results support the importance of salmon runs to the nutritional ecology of stream-dwelling fishes.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS2011

Salmon carcasses increase stream productivity more than inorganic fertilizer pellets: A test on multiple trophic levels in streamside experimental channels

Inorganic nutrient amendments to streams are viewed as possible restoration strategies for re-establishing nutrients and stream productivity throughout the western coast of North America, where salmon runs and associated marine-derived nutrient subsidies have declined. In a mesocosm experiment, we examined the short-term (6 weeks) comparative effects of artificial nutrient pellets and salmon carcasses, alone (low and high amounts) and in combination, on stream food webs. Response variables included dissolved nutrient concentrations, biofilm ash-free dry mass (AFDM) and chlorophyll- a levels, macroinvertebrate density, growth and body condition of juvenile coho salmon Oncorhynchus kisutch , and whole-body lipid content of invertebrates and juvenile coho salmon. Most of the response variables were significantly influenced by carcass treatment; the only response variable significantly influenced by fertilizer pellet treatment was soluble reactive phosphorus (SRP) concentration. Ammonium-nitrogen concentration was the only response variable affected by both (low and high) levels of carcass treatment; all others showed no significant response to the two carcass treatment levels. Significant treatment × time interactions were observed for all responses except nitrate; for most responses, significant treatment effects were detected at certain time periods and not others. For example, significantly higher SRP concentrations were recorded earlier in the experiment, whereas significant fish responses were observed later. These results provide evidence that inorganic nutrient additions do not have the same ecological effects in streams as do salmon carcasses, potentially because inorganic nutrient additions lack carbon-based biochemicals and macromolecules that are sequestered directly or indirectly by consumers. Salmon carcasses, preferably deposited naturally during spawning migrations, appear to be far superior to inorganic nutrient amendments for sustaining and restoring stream productivity, including fish production, and should be chosen over artificial nutrient additions when feasible and practical.

Alaska↗

USGS2011

Identification of marine-derived lipids in juvenile coho salmon and aquatic insects through fatty acid analysis

The energetic benefits enjoyed by consumers in streams with salmon runs depend on how those benefits are accrued. Adult Pacific salmon Oncorhynchus spp. deliver significant amounts of nutrients (i.e., nitrogen and phosphorus) and carbon to streams when they spawn and die; these nutrient additions can have demonstrable effects on primary production in streams. Consumption of carcass tissues or eggs provides for direct energy subsidies to consumers and may have significant effects on their condition. In this study, comparisons of juvenile coho salmon O. kisutch and aquatic insects exposed to terrestrial and marine energy sources demonstrated that direct consumption of marine-derived lipids had a significant effect on the lipid reserves of consumers. Direct consumption of marine-derived tissues was verified through fatty acid analysis. Selected aquatic insects and juvenile coho salmon were reared for 6 weeks in experimental streams supplied with terrestrial or marine energy sources. Chironomid midges, nemourid stoneflies, and juvenile coho salmon exposed to the marine energy source altered their fatty acid compositions by incorporating the long-chain polyunsaturated fatty acids that are characteristic of marine fish. The fatty acid composition of baetid mayflies was unaffected. The direct movement of specific fatty markers indicated that direct consumption of marine-derived tissues led to increased energy reserves (triacylglycerols) in consumers. Similar results were obtained for juvenile coho salmon sampled from natural streams before and after the arrival of adult salmon runs. These data indicate that marine-derived lipids from anadromous fish runs are an important source of reserve lipids for consumers that overwinter in streams.

Transactions of the American Fisheries Society↗