Search for: All records

Some biological invasions can result in algae blooms in the nearshore of clear lakes. We studied if an invasive crayfish (Pacifastacus leniusculus) modified the biomass and community composition of benthic macroinvertebrates and therefore led to a trophic cascade resulting in increased periphyton biomass, elevated littoral primary productivity, and benthic algae bloom in a lake with remarkable transparency [Crater Lake, Oregon, USA]. After quantifying the changes in the spatial distribution of invasive crayfish over a 13-year period, we compared biomass and community composition of littoral–benthic macroinvertebrates, periphyton biovolume, community composition, nutrient limitation, and the development of benthic algae bloom in locations with high and low crayfish density. In addition, we determined if the alteration in community structure resulted in directional changes to gross primary production and ecosystem respiration. The extent of crayfish distribution along the shoreline of Crater Lake doubled over a 13-year period, leaving less than 20% of the shoreline free from crayfish. At high crayfish density sites, benthic macroinvertebrate biomass was 99% lower, and taxa richness was 50% lower than at low crayfish areas. High crayfish sites show tenfold greater periphyton biovolume, sixfold higher periphyton biomass (chlorophylla), twofold higher metabolic productivity, and the presence of large filamentous algae (Cladophorasp.). The invasion of crayfish had negative consequences for a lake protected under the management of the USA National Park Service, with direct impacts on many levels of ecological organization.

 

Wildfire smoke often covers areas larger than the burned area, yet the impacts of smoke on nearby aquatic ecosystems are understudied. In the summer of 2018, wildfire smoke covered Castle Lake (California, USA) for 55 days. We quantified the influence of smoke on the lake by comparing the physics, chemistry, productivity, and animal ecology in the prior four years (2014–2017) to the smoke year (2018). Smoke reduced incident ultraviolet-B (UV-B) radiation by 31% and photosynthetically active radiation (PAR) by 11%. Similarly, underwater UV-B and PAR decreased by 65 and 44%, respectively, and lake heat content decreased by 7%. While the nutrient limitation of primary production did not change, shallow production in the offshore habitat increased by 109%, likely due to a release from photoinhibition. In contrast, deep-water, primary production decreased and the deep-water peak in chlorophylladid not develop, likely due to reduced PAR. Despite the structural changes in primary production, light, and temperature, we observed little significant change in zooplankton biomass, community composition, or migration pattern. Trout were absent from the littoral-benthic habitat during the smoke period. The duration and intensity of smoke influences light regimes, heat content, and productivity, with differing responses to consumers.

 

Abstract Fire is an integral component of ecosystems globally and a tool that humans have harnessed for millennia. Altered fire regimes are a fundamental cause and consequence of global change, impacting people and the biophysical systems on which they depend. As part of the newly emerging Anthropocene, marked by human-caused climate change and radical changes to ecosystems, fire danger is increasing, and fires are having increasingly devastating impacts on human health, infrastructure, and ecosystem services. Increasing fire danger is a vexing problem that requires deep transdisciplinary, trans-sector, and inclusive partnerships to address. Here, we outline barriers and opportunities in the next generation of fire science and provide guidance for investment in future research. We synthesize insights needed to better address the long-standing challenges of innovation across disciplines to (i) promote coordinated research efforts; (ii) embrace different ways of knowing and knowledge generation; (iii) promote exploration of fundamental science; (iv) capitalize on the “firehose” of data for societal benefit; and (v) integrate human and natural systems into models across multiple scales. Fire science is thus at a critical transitional moment. We need to shift from observation and modeled representations of varying components of climate, people, vegetation, and fire to more integrative and predictive approaches that support pathways towards mitigating and adapting to our increasingly flammable world, including the utilization of fire for human safety and benefit. Only through overcoming institutional silos and accessing knowledge across diverse communities can we effectively undertake research that improves outcomes in our more fiery future.