The effects of an Arctic winter on benthic invertebrates in the littoral zone of Char Lake, Northwest Territories

1985 ◽  
Vol 63 (12) ◽  
pp. 2825-2834 ◽  
Author(s):  
Daniel Andrews ◽  
Frank H. Rigler
Keyword(s):  
Northwest Territories ◽  
Benthic Invertebrates ◽  
Littoral Zone ◽  
Growth Efficiency ◽  
Reproductive Period ◽  
Life Cycles ◽  
Conclusive Evidence ◽  
Subzero Temperatures ◽  
Program Temperature ◽  
Population Energetics

A method was devised for sampling the frozen benthos in the littoral zone of Char Lake, Northwest Territories, a polar lake that was studied during the International Biological Program. Temperature probes indicated that during the winter benthic invertebrates in sediments at 0.5 and 1.75 m were exposed to temperatures as low as −18 and −8 °C, respectively. Mortality in animals that had overwintered in the frozen samples ranged from 13 to 84% (mean 46%) and was attributed mostly to sample processing. With the possible exception of chironomids, no conclusive evidence was found that benthic invertebrates avoid freezing by emigrating to deeper portions of the lake. Exposure to subzero temperatures for 8 months or more increased the synchrony in development of the population of the harpacticoid Attheyella nordenskioldii and shifted its peak reproductive period by about 4 months. These changes implied increases in the population's gross production, growth efficiency, and ecological efficiency. The exposure of shallow-dwelling benthic invertebrates to subzero temperatures is a widespread phenomenon, the effects of which on life cycles and population energetics are poorly known.

Spatial and temporal variation in littoral-zone benthic invertebrates from three south-central Ontario lakes

1995 ◽  
Vol 52 (7) ◽  
pp. 1406-1420 ◽  
Author(s):  
R. A. Reid ◽  
K. M. Somers ◽  
S. M. David
Keyword(s):  
Temporal Variation ◽  
Benthic Invertebrates ◽  
Seasonal Changes ◽  
Littoral Zone ◽  
Spatial And Temporal Variation ◽  
South Central ◽  
Temporal Factors ◽  
Follow Up Studies ◽  
Spatial Differences

Surveys of benthic invertebrates have revealed patterns attributed to the impacts of acid deposition. Unfortunately, these patterns may be confounded by temporal variation that will affect follow-up studies of the recovery of these communities. Here, we assess spatial and temporal variation in time-limited, kick-and-sweep collections of littoral-zone benthos. Spatial variation comprised five sites representing the predominant nearshore substrates in each of three lakes. Temporal variation spanned a different scale in each lake with five sites sampled: (i) twice on the same day, (ii) once a week for 3 weeks, and (iii) four times through the ice-free season. Variation was quantified using a model II analysis of variance. Spatial differences predominated in same-day samples (60.4% of the variation on average) and those collected over a 3-week period (46.1%). In contrast, samples collected over the ice-free season revealed that spatial and temporal factors accounted for 9.4 and 25.6% of the variation. We conclude that our collections of littoral macrobenthos are highly repeatable if sampling is restricted to short periods (e.g., 3 weeks). Surveys spanning longer periods may incorporate considerable temporal variation from seasonal changes in abundance.

Energy budgets and reproductive ecologies of mayflies occupying disparate thermal environments

1989 ◽  
Vol 67 (11) ◽  
pp. 2782-2791 ◽  
Author(s):  
Michael J. Benton
Keyword(s):  
Body Size ◽  
Reproductive Effort ◽  
Energy Content ◽  
Aquatic Insect ◽  
Handling Time ◽  
Growth Efficiency ◽  
Life Cycles ◽  
Energy Budgets ◽  
Insect Larvae ◽  
Growth Ratio

Energy budgets were calculated for two populations of Ameletus occupying thermally disparate habitats. Growth, consumption, respiration, fecundity, and energy content of larvae and eggs were determined experimentally. Respiration rates increased and decreased with temperature throughout the life cycles of both species, although thermal effects became less pronounced with increased body size. Ameletus similior exhibited more uniform and consistently higher respiration values than Ameletus celer. Respiration costs were not constant over the life cycle of either species as has been reported for some other mayflies. Growth was influenced by both temperature (which affected instar duration) and body size (which affected growth ratio). Growth corresponded positively to temperature in both species, but was more uniform in A. celer. Net growth efficiency and assimilation were highest during cold periods in A. celer, but highest during warmer periods in A. similior. Consumption estimates were high even after adjustments for projected nonfeeding time, but unless food availability or handling time is limiting, the feeding rate of Ameletus relative to body mass may be higher than rates reported for other aquatic insect larvae. Several sources of error in consumption estimates existed, however. Assimilation efficiencies were low, but comparable to those for other herbivorous aquatic insects. Reproductive effort was higher in A. celer, but net reproductive effort was lower. The higher net reproductive effort by A. similior did not result in increased fecundity as expected, but in higher egg energy content. This and other factors suggest that A. similior displays more "K-selected" traits than A. celer, and indicates that greater fitness may not necessarily be synonymous with higher fecundity in all mayflies in all habitats.

scholarly journals ­Reproductive strategies of two common sympatric Mediterranean sponges:Dysidea avara(Dictyoceratida) andPhorbas tenacior(Poecilosclerida)

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5458 ◽  
Author(s):  
Sonia de Caralt ◽  
Janina González ◽  
Xavier Turon ◽  
María J. Uriz
Keyword(s):  
Reproductive Effort ◽  
Reproductive Traits ◽  
Reproductive Period ◽  
Life Cycles ◽  
Life Strategy ◽  
Larval Size ◽  
Dysidea Avara ◽  
Species Specific ◽  
June July ◽  
Benthic Ecosystems

Despite their abundance in benthic ecosystems, life cycles and reproductive features of most sponge species remain unknown. We have studied the main reproductive features of two demosponges,Dysidea avaraandPhorbas tenacior,belonging to phylogenetically distant groups: Orders Dictyoceratida and Poecilosclerida, respectively. Both sponges are abundant and share habitat in the Mediterranean rocky sublittoral. They brood parenchymella larvae with different morphology and behaviour. Sampling was conducted monthly over a two-year period in a locality where both species coexist. The two species reproduced in spring-summer, and presented species-specific reproductive features despite being subject to the same environmental conditions.D. avarahas a shorter reproductive period thanP. tenacior, ending before the peak of temperature in summer, while the reproductive period ofP. tenaciorlasts until beginning of autumn. Brooding larvae were present in June-July inD. avara, and in August-October inP. tenacior. Larval size, reproductive effort and number of larvae produced (measured the month with the maximum production) were significantly higher inD. avarathan inP. tenacior. A higher reproductive effort and larval traits point to a more opportunistic life strategy inD. avarathan inP. tenacior.A lack of overlap in the timing of larval release, as well as different reproductive traits, may reduce competition and facilitate the coexistence of these two sympatric and abundant sponges.

scholarly journals Life-history strategies of calanoid congeners under two different climate regimes: a comparison

2004 ◽  
Vol 61 (4) ◽  
pp. 709-720 ◽  
Author(s):  
Claudia Halsband-Lenk ◽  
François Carlotti ◽  
Wulf Greve
Keyword(s):  
Life History ◽  
North Sea ◽  
Life History Traits ◽  
Reproductive Period ◽  
Life Cycles ◽  
Life History Strategies ◽  
The North ◽  
Temperature Regimes ◽  
Shelf Sea ◽  
The North Sea

Abstract To evaluate the relationship between different environmental temperature regimes and life-history traits of key planktonic taxa, the life cycles of congener pairs of Temora and Centropages species at two sites, a cold-temperate shelf sea (Helgoland Island, North Sea) and a warm-temperate oceanic site (Bay of Villefranche, Mediterranean) were compared in a multi-annual time-series. In an attempt to assemble a variety of parameters – some detailed, others sporadically measured – a synthesis of the life cycle is presented for each population. Although closely related, congeners showed distinct temperature preferences and specific adaptations of their life cycles to temperature regime. On the other hand, co-existing species such as T. longicornis and C. hamatus in the North Sea showed some analogous life-history traits. C. typicus occupied an intermediate position and was able to tolerate both temperature regimes by shifting its reproductive period between seasons. We point out interannual and inter-site variability in the populations investigated and identify the unsolved questions in regard to the seasonal dynamics of these species that require verification.

Ecology of Chironomidae (Diptera) in a Polar Lake

1976 ◽  
Vol 33 (2) ◽  
pp. 227-247 ◽  
Author(s):  
H. E. Welch
Keyword(s):  
Energy Flow ◽  
Growth Efficiency ◽  
Life Cycles ◽  
Egg Laying ◽  
Larval Life ◽  
Metabolic Compensation ◽  
Class Strength ◽  
Growth Respiration ◽  
Definition Of

The six common genera of Chironomidae (Diptera) in Char Lake, Resolute, Northwest Territories (74°42′N lat.) were studied intensively from 1969 to 1972. Heterotrissocladius oliveri and a Trissocladius species are characteristic of the sediment zone, while two species of Orthocladius, Pseudodiamesa arctica, Paracladius quadrinodosus, and Lauterbornia sp. are restricted mainly to the rocky and moss zones. Life cycles are 2 or 3 yr, depending upon the species. Year-classes could be discriminated by instar frequency distribution. Populations increased steadily during the study period, for an average increase in strength of 5 times between the 1968 and 1971 year-classes. Summer emergence and egg-laying conditions are of overriding importance to year-class strength. Mortality within year-classes is undetectable until the last 4 mo of larval life, when mortality due to char predation is about 65% between April and the time of emergence. The physiology of these chironomids does not seem unusual aside from continuing activity down to 0 C, and there is no indication of metabolic compensation. Net growth efficiency averages 36%. Assimilated energy (growth + respiration) at 8.6 kcal m−2 yr−1 is very low compared with temperate zone populations, but is more similar as a percent of photosynthesis, 4.1%. The relatively large detritus pool and the presence of both 2- and 3-yr species tend to stabilize chironomid energy flow. Definition of long-term averages for chironomid populations in Char Lake would require a decade or more of study.

scholarly journals Persistent shift of Calanus spp. in the southwestern Norwegian Sea since 2003, linked to ocean climate

2015 ◽  
Vol 73 (5) ◽  
pp. 1319-1329 ◽  
Author(s):  
Inga Kristiansen ◽  
Eilif Gaard ◽  
Hjálmar Hátún ◽  
Sigrún Jónasdóttir ◽  
A. Sofia A. Ferreira
Keyword(s):  
Phytoplankton Bloom ◽  
Dominant Role ◽  
Atlantic Water ◽  
Reproductive Period ◽  
Life Cycles ◽  
Water Masses ◽  
Calanus Finmarchicus ◽  
The Arctic ◽  
Arctic Water ◽  
Norwegian Sea

Abstract The southwestern Norwegian Sea is characterized by an inflow of warm and saline Atlantic water from the southwest and cold and less saline East Icelandic Water (EIW), of Arctic origin, from the northwest. These two water masses meet and form the Iceland-Faroe Front (IFF). In this region, the copepod Calanus finmarchicus plays a key role in the pelagic ecosystem. Time-series of C. finmarchicus and Calanus hyperboreus in May and September, extending back to the early 1990s, were studied in relation to phytoplankton bloom dynamics and hydrography. The main reproductive period of C. finmarchicus started consistently earlier south of the IFF, resulting in different life cycles and stage compositions in the two water masses. In 2003, a sudden shift occurred north of the IFF, resulting in a similar phenology pattern to south of the IFF. Before this, only one generation of C. finmarchicus was produced in the Arctic water, but the earlier reproduction enabled the species to produce two generations after 2003. Simultaneously, C. hyperboreus, an expatriate in the EIW, largely disappeared. Food availability is unlikely the reason for the phenological differences observed across the front, as the typical pattern of the phytoplankton spring bloom showed an earlier onset north of the IFF. Temperature and salinity peaked at record high values in 2003 and 2004, and therefore possible links to oceanography are discussed. The dominant role of Calanus spp. and the potential linkages to water mass exchanges may herald strong effects on the ecosystem and pelagic fish in this subpolar Atlantic region under expected climate change.

scholarly journals Observations on the origin and fate of flagellated gametes in multiple tests of discorbis (foraminifera)

1940 ◽  
Vol 24 (1) ◽  
pp. 201-225 ◽  
Author(s):  
Earl H. Myers
Keyword(s):  
Life Cycle ◽  
Genetic Relationship ◽  
Life Cycles ◽  
Conclusive Evidence ◽  
Coralline Algae ◽  
Multiple Tests ◽  
Relationship Of

It has long been presumed that the gametes of certain Foraminifera are flagellated; however, the lack of conclusive evidence as to the origin and fate of these flagellated gametes has made their existence problematical.In syzygous species of Discorbis the gametes are flagellated and the genetic relationship of these gametes is easily demonstrated, since gametogenesis, fertilization, and the development of two- and three-chambered multinucleate microspheric agamonts takes place within the excavated tests of two or more mononucleate megalospheric gamonts associated in syzygy.The life cycle of Discorbis herein described is in general agreement with the life cycle of Polystomella crispa proposed by J. J. Lister, and completes an interesting series of life cycles in which a progressive modification in behaviour and test morphology can be traced.Behaviour, ecology, and distribution of four syzygous species of Discorbis are discussed.Multiple tests of these syzygous species of Foraminifera can be found in most rock-bottomed tide pools that supports a growth of coralline algae. These sexual groups provide a sure source of material for the demonstration of flagellated gametes in the Foraminifera.

Seedling regeneration at northern treeline, Northwest Territories tundra

2019 ◽  
Author(s):  
Emily Grishaber
Keyword(s):  
Northwest Territories ◽  
Physical Environment ◽  
Seed Viability ◽  
Growth Conditions ◽  
Conclusive Evidence ◽  
Reproductive Capacity ◽  
Limiting Factor ◽  
Mature Trees ◽  
Plant Matter ◽  
Site Characteristics

Global warming has had an amplified effect in northern environments (i.e. Arctic and Subarctic regions). An indirect result of this warming is what is known as Arctic greening, which is the increase of photosynthetic material, or plant matter, in Arctic environments. How this greening trend is represented by trees at latitudinal (or northern) treeline is largely unknown. To determine how treeline may respond, I am investigating the physical environment surrounding seedlings found growing at treeline in the Northwest Territories, as well as the reproductive capacity of the mature trees in this region. Physical characteristics of sites which contain seedlings are compared to sites within the same region which do not in an attempt to determine what aspects of these environments are significant in the establishment of seedlings at treeline. Site characteristics include vegetation cover, distance to mature trees, and distance and dimensions of the nearest shrub. Reproductive capacity of mature trees is also tested to determine how significant seed viability may be in generating seedlings in this region. The limiting factor in treeline expansion may be an issue of pre-dispersal (i.e. viable seed production) as opposed to post-dispersal (i.e. seedling growth). I am conducting a germination test where I have extracted seeds from fifteen trees dispersed throughout the treeline region and have placed them under ideal growth conditions for an honest depiction of viable to unviable seed ratios. These tests may show conclusive evidence regarding what factors are contributing to treeline dynamics within a changing environment.

Life histories of benthic invertebrates in a kauri forst stream in northern New Zealand

1981 ◽  
Vol 32 (2) ◽  
pp. 191 ◽  
Author(s):  
DR Towns
Keyword(s):  
New Zealand ◽  
Benthic Invertebrates ◽  
Life Histories ◽  
Model Comparison ◽  
Benthic Invertebrate ◽  
Potamopyrgus Antipodarum ◽  
Life Cycles ◽  
Invertebrate Species ◽  
Paracalliope Fluviatilis

Life histories of the following 12 benthic invertebrate species were investigated at four sites in the Waitakere River: Potamopyrgus antipodarum (Gastropoda : Hydrobiidae); Paracalliope fluviatilis (Amphipoda : Eusiridae), Zephlebia (Neozephlebia) sp. and Deleatidium spp. (Ephemeroptera : Leptophlebiidae), Hydora nitida (Coleoptera : Elmidae), Maoridiamesa harrisi, ?Austrocladius sp. and Paratanytarsus agameta (Diptera : Chironomidae), Austrosimulium australense (Diptera : Simuliidae), Aoteapsyche colonica (Trichoptera : Hydropsychidae), Oxyethira albireps (Trichoptera : Hydroptilidae), and Olinga feredayi (Trichoptera : Conoesucidae). All species had life cycles which were non-seasonal according to the Hynes model. Comparison with recent studies in southern North Island and South Island streams suggests that non-seasonal life cycles predominate in New Zealand streams.

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