Does the presence of burrowing seabirds increase local invertebrate abundance?

The ash-free dry mass (AFDM) of detritus, invertebrates, and algae in the diet of juvenile white sucker (Catostomus commersoni) was determined by quantitative microscopy. Fish were collected from a northern Michigan pond from January through October 1986 and their seasonal diet was compared with benthc invertebrate abundance. The quantity of detritus in sucker foreguts was inversely related to benthic microcrustacean densities. In July, microcrustacean densities were high and they comprised 95% of the AFDM in foregut contents. By October, microcrustacean densities had declined to 13% of their maximum density and detritus comprised over 90% of the sucker's diet AFDM. In laboratory aquaria, sucker that were fed detritus mixed with four different densities of Artemia ingested significantly more detritus from diets that provided lower Artemia densities. In the presence of high Artemia densities, sucker completely rejected detritus and ingested only Artemia, The fact that juvenile sucker can separate detritus from invertebrates that they swallow demonstrates that detritus is not ingested incidentally. Both laboratory and field data support the hypothesis that detritus is ingested intentionally when preferred invertebrate prey are scarce.

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Aquatic Invertebrate Abundance in Relation to Changing Marsh Vegetation

The American Midland Naturalist ◽

10.2307/2424396 ◽

1976 ◽

Vol 95 (2) ◽

pp. 313 ◽

Cited By ~ 98

Author(s):

David K. Voigts

Keyword(s):

Aquatic Invertebrate ◽

Marsh Vegetation ◽

Invertebrate Abundance

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Detecting predation of a burrow-nesting seabird by two introduced predators, using stable isotopes, dietary analysis and experimental removals

Wildlife Research ◽

10.1071/wr07037 ◽

2007 ◽

Vol 34 (6) ◽

pp. 443 ◽

Cited By ~ 16

Author(s):

Grant A. Harper

Keyword(s):

Rattus Rattus ◽

Isotopic Analysis ◽

Diet Analysis ◽

Passerine Birds ◽

Dietary Analysis ◽

Stable Isotopic Analysis ◽

Introduced Predators ◽

Ship Rat ◽

Stable Isotopic ◽

Burrowing Seabirds

Burrowing seabirds are vulnerable to extirpation by introduced predators such as rats, but much evidence of predation is circumstantial. On Taukihepa, an island off southern New Zealand, two possible predators exist with sooty shearwaters (Puffinus griseus): the weka (Gallirallus australis), a large rail, and the ship rat (Rattus rattus), both introduced to the island. It was expected that chick predation would be principally by weka, the much larger of the two predators. To measure losses of sooty shearwater chicks to weka or rats, nests were monitored with burrow-scopes at six sites in the summers of 2003–04 and 2004–05. In three of the sites rats were removed on 4-ha grids by trapping. In the other three sites rats were not trapped. In addition, weka were removed from all six sites in 2005. Concurrent diet analysis of weka and rat stomachs was undertaken as well as stable isotopic analysis (δ13C, δ15N) of samples from rats and weka. These were compared with possible prey items including sooty shearwaters. Additional stable isotope samples were taken from Pacific rats (Rattus exulans), a small rat species present with weka and sooty shearwaters on nearby Moginui Island. Weka diet comprised ~40% of bird remains by volume and calculations using Isosource, an isotopic source portioning model, estimated sooty shearwaters contributed 59% (range: 15–71%) of weka diet during the sooty shearwater chick-raising period. Ship rats, in contrast, had very depleted δ13C isotope signatures compared with sooty shearwaters and bird remains contributed <9% of diet by volume, with Isosource calculations suggesting that ship rats consumed more passerine birds (mean: 30%; range 5–51%) than sooty shearwaters (mean 24%; range: 0–44%). In both summers, more chicks were lost on sites from which rats had been removed than on control sites. When weka were removed in 2005, fewer chicks were lost than in 2004 and significantly fewer weka-killed chicks were found on weka-removal sites than on non-removal sites. Weka were the principal predator of sooty shearwater chicks, depredating an estimated 9.9% of nests. Combining several techniques quantified the loss and identified the principal predator of a seabird in decline.

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Effects of micro-, meio- and macroinvertebrates associated with burial on the decomposition of an aquatic macrophyte (Vallisneria natans) in a eutrophic shallow lake in China

Marine and Freshwater Research ◽

10.1071/mf18148 ◽

2019 ◽

Vol 70 (4) ◽

pp. 554

Author(s):

Shaojun Chen ◽

Dong Wang

Keyword(s):

Aquatic Invertebrates ◽

Microbial Respiration ◽

Aquatic Macrophyte ◽

Mesh Size ◽

Relative Importance ◽

Vallisneria Natans ◽

Plant Decomposition ◽

Invertebrate Abundance ◽

Average Contribution

Aquatic invertebrates play an important role in plant decomposition. However, little information is available regarding the relative importance of micro-, meio- and macroinvertebrates in this process, particularly their role in the decomposition of buried organic matter. To investigate the role of these invertebrates in the decomposition of the aquatic macrophyte Vallisneria natans, leaves of V. natans were placed in litterbags with four different mesh sizes (0.025, 0.042, 0.5 and 5mm) and the bags were either incubated at the sediment–water (SW) interface or buried at a depth of 10cm (B10) for 60 days in Lake Nanhu, China, in July 2015. Increased mesh size significantly increased the loss of plant mass. The decomposition rate ranged from 0.0173 to 0.0467day–1 in the SW treatment, and from 0.0083 to 0.0280day–1 in the B10 treatment. Excluding microinvertebrates, burial significantly affected microbial respiration and invertebrate abundance. Increased mesh size increased invertebrate abundance and richness, but did not significantly affect microbial respiration in either treatment. The average contribution of micro-, meio- and macroinvertebrates and microbes to plant mass loss in the SW treatment was 23.1, 13.5, 7.0 and 56.5% respectively, compared with 19.7, 24.5, 12.3 and 43.5% respectively in the B10 treatment. The results of this study reveal the important but underestimated role of micro- and meioinvertebrates in macrophyte decomposition.

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Separating the effects of habitat amount and fragmentation on invertebrate abundance using a multi-scale framework

Landscape Ecology ◽

10.1007/s10980-018-0748-3 ◽

2018 ◽

Vol 34 (1) ◽

pp. 105-117 ◽

Cited By ~ 7

Author(s):

Laura Bosco ◽

Ho Yi Wan ◽

Samuel A. Cushman ◽

Raphaël Arlettaz ◽

Alain Jacot

Keyword(s):

Habitat Amount ◽

Multi Scale ◽

Invertebrate Abundance

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The effects of riparian forestry on invertebrate drift and brown trout in upland streams of contrasting acidity

Hydrology and Earth System Sciences ◽

10.5194/hess-8-578-2004 ◽

2004 ◽

Vol 8 (3) ◽

pp. 578-588 ◽

Cited By ~ 15

Author(s):

S. J. Ormerod ◽

M. E. Jones ◽

M. C. Jones ◽

D. R. Phillips

Keyword(s):

Land Use ◽

Brown Trout ◽

Salmo Trutta ◽

Benthic Invertebrate ◽

Acid Sites ◽

Invertebrate Drift ◽

Conifer Forest ◽

Terrestrial Invertebrates ◽

Invertebrate Abundance ◽

Drift Density

Abstract. Variations in macroinvertebrate drift and benthic invertebrate abundance were assessed in 30 upland Welsh streams of varying acidity (pH < 5.7 or pH.> 6.0) and riparian land-use (conifer, moorland or native broadleaf). The consequences for the diet and condition of wild brown trout Salmo trutta were also assessed. As expected from previous studies, there were significant reductions in benthic invertebrate abundance, aquatic drift density (by >60%), aquatic drift biomass (by >35%), total drift density (by >35%) and total drift biomass (by >20%) at acid sites by comparison with circumneutral sites due largely to the scarcity of mayflies. Absolute drift from terrestrial sources was unrelated to stream pH but formed a significantly greater proportion of total drift at acid sites (30-65% of density) than at circumneutral sites (20-40%) as aquatic contributions declined. Most of this apparent land use effect reflected significantly increased terrestrial drift under broadleaves. There was no significant reduction in terrestrial or aquatic drift at conifer forest sites per se after accounting for low pH. Trout diet varied substantially between locations partly reflecting variations in drift: significantly fewer mayflies and stoneflies were eaten at acid sites, and significantly more terrestrial prey were eaten under broadleaves. However, acidity did not reduce trout condition or gut-fullness. Unexpectedly, trout condition was significantly enhanced at conifer sites, irrespective of their pH. Hence, acidity has greater effects on the benthic abundance and drift density of invertebrates in upland streams than does riparian land use. However, trout forage flexibly enough to offset any possible food deficit, for example by switching to chironomids and terrestrial invertebrates. Enhanced terrestrial contributions to invertebrate drift from riparian broadleaf trees may be important in supplementing foraging opportunities for trout where aquatic prey are scarce. These data illustrate the value of native tree species in riparian locations in upland Britain and the energy subsidy they provide might well be disproportionately important for otherwise impoverished acid streams Keywords: brown trout, land-use, acidification, drift, forestry, streams

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Structural Complexity and Distance from Source Habitat Determine Invertebrate Abundance and Diversity

Biotropica ◽

10.1111/j.1744-7429.2011.00762.x ◽

2011 ◽

Vol 43 (6) ◽

pp. 738-745 ◽

Cited By ~ 21

Author(s):

Roger P. Mormul ◽

Sidinei M. Thomaz ◽

Alice M. Takeda ◽

Rômulo D. Behrend

Keyword(s):

Structural Complexity ◽

Invertebrate Abundance ◽

Abundance And Diversity

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