CLUSTER ANALYSIS AND WATER PROJECT EVALUATION1

Large-scale water projects have long been undertaken for the benefit of people. Information appears to be needed as to who benefits as a result of these projects. The hypothesis was tested that regional income and employment benefits would be closely related to areas where water projects were located. The analytical procedure centered on cluster analysis used to delineate counties in the Tennessee River Watershed on the basis of changes in selected variables over different periods. The hypothesis was rejected. It was concluded that benefits of water projects were not necessarily confined to isolated areas near projects but were regional.     

Embryonic and parental preferences for incubation temperature in herring gulls: implications for parent-offspring conflict

According to Trivers (1974), parent-offspring (P-O) conflict arises because offspring are selected to solicit more care than parents are selected to provide. However, should benefits fail to increase with increasing care, the offspring optimum can be reduced to the point where predicted P-O conflict vanishes. We examined offspring demand and parental care in such a benefit-limited system in herring gulls (Larus argentatus). In this species, parents typically neglect their lasthatched (C-) egg during the final hours of hatching (pipped-egg stage), allowing mean temperature to drop by about 4°C, to near 33°C. Other studies indicate that no increased offspring benefit arises from increasing pipped egg incubation temperature above that level, but embryo damage occurs if temperature drops lower. In such a system, P-O conflict over preferred incubation temperature is predicted to be minimal or absent. We assessed phenotypic manifestations of conflict by determining incubation temperature preferences of parent and offspring independently. Temperature provided solely by parental initiative was 33.9°C (artificial eggs, corrected for embryonic heat production). Preferred incubation temperature of pipped embryos was measured by exposing them to moderate chilling (20°C) punctuated by 4-min periods of rewarming when they called. Temperature of vocally thermoregulating embryos stabilized around a mean of 32.9–33.4°C, about 0.5–1.0°C below parental preference. Acting independently, parents and embryos each maintained egg temperature at or near minimum developmentally safe levels. Results provided no evidence for phenotypic conflict, as predicted by a benefit-limited version of Trivers' P-O conflict model. Benefit limitation may also be relevant to P-O conflict in other contexts such as feeding of newly-hatched young.     

New development in the MOCNESS,an apparatus for sampling zooplankton and micronekton

Four variants of the Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS) have been constructed to sample a broad size spectrum of oceanic animals from microzooplankton to micronekton. The systems differ in mouth opening dimensions (ranging from 1/4 to 20 m²), the number of nets carried (from 5 to 20), and the mesh size of the netting (from 64 m to 3.0 mm). A new electronics package enables an operator to send commands down a single conductor, armored cable to open/close the nets and provides 12-bit resolution for the environmental (temperature, depth, conductivity) and net operation data (flow, net-frame angle, net-bar release), which are transmitted up the cable to the deck unit at 2-s intervals. A microcomputer system, interfaced to the deck unit, calculates salinity, volume filtered by a net, net trajectory velocity, and vertical velocity. The data are printed out and stored on disc, and profiles of temperature and salinity versus depth are plotted during the course of the tow. Analysis of the relationship between the geometry of the MOCNESS under tow and the past and present methods used to estimate the water filtered by a net revealed that significant bias is introduced when the ascent or descent angle of a net is disregarded. The bias is a function of the ratio of vertical velocity to net trajectory velocity and results in an underestimate of volume filtered while shooting a net and an overestimate while hauling.     

Direct measurement of dissolved organic carbon release by phytoplankton and incorporation by microheterotrophs

It is now possible to divide particulate primary production into algal and heterotrophic components without physical separation. This depends on two innovations, the introduction of isotope in the form of labelled dissolved product(s) of primary production and the employment of a data analysis specifically designed for tracer kinetic incorporation experiments. The ¹⁴C technique described by Steemann Nielsen (1952) is inapplicable in the analyses of certain classes of systems and kinetic tracer incorporation experiments must be employed instead. We show that measurement of PDOC production rate requires such kinetic tracer analyses. Measurements made in the laboratory on water taken from 2 m depth in South West Arm of the Port Hacking estuary showed that: (1) the steady-state rate of PDOC production was 0.10 to 0.13 mg C.m^-3.h^-1; (2) the rate of PDOC incorporation into microheterotroph particulate organic carbon was 0.10 to 0.12 mg C.m^-3.h^-1; (3) the rate at which PDOC was respired to CO₂ was 0.001 to 0.003 mg C.m^-3.h^-1. (4) the PDOC makes up only about 0.1% of the total dissolved organic carbon. The size class of particles associated with PDOC production differed from the size class responsible for uptake of PDOC. More than 50% of the PDOC production was associated with particles having a nominal diameter range of 20 to 63 m, while this fraction was responsible for <10% of the incorporation.     

Temporal and spatial relationships in fine particle strong acidity, sulphate, PM1O, and PM2.5 across multiple canadian locations

The Canadian Acid Aerosol Measurement Program (CAAMP) was established in 1992 to gain a better understanding of the atmospheric behaviour of fine particle strong acidity (“acid aerosols”) and to facilitate an assessment of the potential health risks associated with acid aerosols and particles in general. During 1992. 1993 and 1994, annular denuder and filter measurements were taken at four sites in Ontario, two in Quebec, three in the Atlantic Provinces and one in the greater Vancouver area. Mean fine particle sulphate concentrations (SO₄²⁻) were highest in southern Ontario (annual average ranged from 40–70 nmol m⁻³), lowest at a site in the Vancouver area (average = 16 nmol m⁻³) and second lowest in rural Nova Scotia. However, mean fine particle strong acid concentrations (H⁺) were geographically different. The highest mean concentrations were at the east coast sites (annual average of up to 30 nmol m⁻³). Acidities were lower in areas where the fine particle acidity experienced greater neutralization from reaction with ammonia. This included the major urban centres (i.e. Toronto and Montréal) and areas with greater amounts of agricultural activity, as in rural southern Ontario. On average, ambient concentrations of fine and coarse particle mass were larger in the urban areas and also in areas where SO₄²⁻ levels were higher. All the particle components were episodic. However, compared to SO₄²⁻ and fine particles (PM_2.5 or PM_2.1, depending upon inlet design), episodes of H⁺ tended to be less frequent and of shorter duration, particularly in Ontario. Saint John, New Brunswick, had the highest mean annual H⁺ concentration, which was 30 nmol m⁻³. H⁺ episodes (24 h concentration > 100 nmol m⁻³) were also the most frequent at this location. The high levels in Saint John were partially due to local sulphur dioxide sources and heterogeneous chemistry occurring in fog, which, on average, led to a 50% enhancement in sulphate, relative to upwind conditions.There was a substantial amount of intersite correlation in the day to day variations in H⁺, SO₄²⁻ , PM_2.5 and PM₁₀ (fine + coarse particles) concentrations, which is due to the influence of synoptic-scale meteorology and the relatively long atmospheric lifetime of fine particles. Sulphate was the most regionally homogenous species. Pearson correlation coefficients comparing SO₄²⁻ between sites ranged from 0.6 to 0.9, depending on site separation and lag time. In many cases, particle episodes were observed to move across the entire eastern portion of Canada with about a two-day lag between the SO₄²⁻ levels in southern Ontario and in southern Nova Scotia.     

Food-dependent benefits of hatching asynchrony in American kestrels Falco sparverius

Food supply and hatching asynchrony were manipulated for 90 broods of American kestrels (Falco sparverius) during 1989–1991. We measured the growth and mortality of nestlings within four treatment groups (asynchronous, synchronous, food-supplemented, unsupplemented) to test the brood reduction hypothesis of Lack (1947, 1954). Fledging success did not differ between synchronous and asynchronous broods when food was poor but consistent with the brood reduction hypothesis, nestlings died at a younger age in asynchronous broods. When food was supplemented, mortality did not occur in the synchronous broods but youngest nestlings still died in asynchronous nests despite apparently adequate food for the brood. Oldest nestlings in asynchronous broods fledged with a greater mass than their younger siblings, also consistent with Lack's hypothesis. Average nestling quality in synchronous broods was very dependent on food levels. Synchronous young that were supplemented were, on average, the heaviest of any treatment group but young from unsupplemented synchronous broods were the lightest. Overall, patterns of mortality and growth for kestrels support the brood reduction hypothesis when food is limited, but not when it is abundant. This food-dependent benefit of asynchrony in the nestling period is a prerequisite for facultatively adjusted hatching spans during laying.     

Coastal and riverine ecosystems as adaptive flood defenses under a changing climate

Adaptation planning for flood risk forms a significant part of global climate change response. Engineering responses to higher water levels can be prohibitively costly. Several recent studies emphasize the potential role of ecosystems in flood protection as adaptive risk reduction measures while also contributing to carbon fixation. Here, we use a conceptual model study to illustrate the built-in adaptive capability of ecosystems to reduce a wide range of wave heights, occurring at different water levels, to a narrower range. Our model shows that wave height of waves running through a forested section is independent of initial height or of water level. Although the underlying phenomenon of non-linear wave attenuation within coastal vegetation is well studied, implications of reducing variability in wave heights for design of ecosystem and levee combinations have not yet been properly outlined. Narrowing the range of wave heights by a vegetation field generates an adaptive levee that is robust to a whole range of external conditions rather than only to a maximum wave height. This feature can substantially reduce costs for retrofitting of levees under changing future wave climates. Thereby, in wave prone areas, inclusion of ecosystems into flood defense schemes constitutes an adaptive and safe alternative to only hard engineered flood risk measures.     

Prey size increases with nestling age: are provisioning parents programmed or responding to cues from offspring?

As offspring grow, parents often feed them with different sizes or taxa of prey to suit the changing nutritional or energetic demands. We investigated whether such changes in prey types were innate and inflexible or whether they were based on the proximate cue of offspring size. We created experimental broods in which parent blue tits Cyanistes caeruleus and pied flycatchers Ficedula hypoleuca received either older nestlings simulating rapid development or younger nestlings simulating delayed development. The size of prey increased over time in all brood types, suggesting a strong programmed pattern of foraging by parents. However, delayed broods were provisioned with smaller prey than control or advanced broods indicating some plasticity in the response by the parents to the size of nestlings. Although female birds brought smaller prey than male birds, both sexes showed the same rate of increase of prey size with time and brought similar types of prey items. The proportion of soft, digestible larva prey in the nestling diet decreased over time in pied flycatchers but increased in blue tits. Counter to the hypothesis that spiders provide unique and preferred nutrients for young nestlings, the proportion of arachnids in the diet did not change with nestling age for either species. The lack of treatment effect on the taxa of prey delivered suggests that temporal shifts in diet composition are not driven by the proximate cues of nestling age or size but that the feeding patterns are fairly innate and fixed in these altricial birds.