Edit document metadata
password
Password for the
Dietrich
collection.
action
edit
document metadata
(below)
delete
this document
(check this box and type password above)
move
or
copy
this document
(check this box and type password above)
title
author
editor
journal
publication date
Month
unknown
January
February
March
April
May
June
July
August
September
October
November
December
Day
unknown
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
notes
1Department of Integrative Biology, University of California–Berkeley, Berkeley, California 94707-3140 USA 2Department of Biology, 1250 Siskiyou Boulevard, Southern Oregon University, Ashland, Oregon 97520 USA 3Department of Earth and Planetary Science,
Any other info that should appear in the information we have about this document.
abstract
Eighteen years of field observations and five summer field experiments in a coastal California river suggest that hydrologic regimes influence algal blooms and the impacts of fish on algae, cyanobacteria, invertebrates, and small vertebrates. In this Mediterranean climate, rainy winters precede the biologically active summer low-flow season. Cladophora glomerata, the filamentous green alga that dominates primary producer biomass during summer, reaches peak biomass during late spring or early summer. Cladophora blooms are larger if floods during the preceding winter attained or exceeded ‘‘bankfull discharge’’ (sufficient to mobilize much of the river bed, estimated at 120 m3/s). In 9 out of 12 summers preceded by large bed-scouring floods, the average peak height of attached Cladophora turfs equaled or exceeded 50 cm. In five out of six years when flows remained below bankfull, Cladophora biomass peaked at lower levels. Flood effects on algae were partially mediated through impacts on consumers in food webs. In three experiments that followed scouring winter floods, juvenile steelhead (Oncorhynchus mykiss) and roach (Lavinia (Hesperoleucas) symmetricus) suppressed certain insects and young-of-the-year fish fry, affecting persistence or accrual of algae positively or negatively, depending on the predator-specific vulnerabilities of primary consumers capable of suppressing algae during a given year. During two post-flood years, these grazers were more vulnerable to small predators (odonates and fish fry, which stocked steelhead always suppressed) than to experimentally manipulated, larger fish, which had adverse effects on algae in those years. During one post-flood year, all enclosed grazers capable of suppressing algae were consumed by steelhead, which therefore had positive effects on algae. During drought years, when no bed-scouring winter flows occurred, large armored caddisflies (Dicosmoecus gilvipes) were more abundant during the subsequent summer. In drought-year experiments, stocked fish had little or no influence on algal standing crops, which increased only when Dicosmoecus were removed from enclosures. Flood scour, by suppressing invulnerable grazers, set the stage for fish mediated effects on algae in this river food web. Whether these effects were positive or negative depended on the predator-specific vulnerabilities of primary consumers that dominated during a given summer.
keywords
algal blooms; Cladophora glomerata; context dependency; effect sizes; flood scour; food chain length; interaction strength; Lavinia (Hesperoleucas) symmetricus; long-term studies; Mediterranean hydrologic regimes; Oncorhynchus mykiss; predator impacts.
project
bibtex entry
Enter a reference in BibTeX format.
Back to
DocuBase
BNHM
University of California, Berkeley