WATERFALL REAERATION IN THE PASSAIC RIVER1

The effects of waterfall-induced turbulence on the dissolved oxygen concentration of the Passaic River (New Jersey) at two mostly natural waterfalls were observed during a five-month period encompassing high to low temperature and flow. A parameter defined by past investigators as the “deficit ratio” was found to be useful for mathematically describing the results. The Great Falls system showed the deficit ratio to be an inverse function of temperature for all events, with good correlation. A relationship was developed for the Little Falls system under low flow showing the deficit ratio to likewise be an inverse function of temperature and a power function of flow.     

BENTHIC INVERTEBRATE RESPONSE TO POLLUTION ABATEMENT: STRUCTURAL CHANGES AND FUNCTIONAL IMPLICATIONS1

We examined changes in certain structural and functional aspects of the benthic invertebrate community in the Penobscot River, Maine, between 1974 and 1981. During this period, two pulp and paper manufacturers and three municipalities spent an estimated $33 million to reduce point source effluents harmful to aquatic life. We developed a biotic index based on objectively derived pollution tolerance values for resident taxa. Analysis of the benthic invertebrate community indicated that substantial improvement in water quality had resulted from pollution abatement. We established a four-group water quality classification scheme based on biotic index ranges, and showed that every site that was not in the best water quality classification in 1974 improved its classification to a better water quality group in 1981, and that the sites in the best group did not change. Relative abundances of functional feeding groups also changed, as were predicted by the river continuum theory. The effluents had acted as a “reset mechanism” that shifted polluted areas from autotrophic to more heterotrophic conditions. The direction of the shift was reversed in response to abatement efforts. Functional analyses of energy dynamics could lead to a more ecologically sound classification of water quality.     

OIL SLICK MOTION NEAR CHESAPEAKE BAY ENTRANCE1

Five-to-50-gallon slicks of No. 6 (Bunker C) fuel oil were tracked for several hours on six different occasions. Slick motion was due mainly to surface currents. The slick wind factor varied with wind speed, showing a threshold at seven knots and approaching 2.0 percent at 20 knots. Published values of 2.3 to 5 percent did not exclude the effects of wind-generated surface currents. Prediction of slick motion using wind and published tidal-current data was deficient; accuracy will require extensive wind and surface-current time-series data.     

Environmental change in the mid-Boteti area of north-central Botswana: Biophysical processes and human perceptions

Increased interest in environmental change issues has led researchers to consider more integrated approaches to change dynamics. This paper examines change in terms of land degradation in north-central Botswana from both biophysical and human perspectives. Although seasonal and periodic droughts were prevalent, analysis of rainfall data over the past 70 years revealed no downward trend. However, indicators of declining productivity such as soil erosion, loss of vegetation cover, and a declining groundwater table were amply evident. The GIS analysis of remotely sensed data has shown that complete vegetation recovery after drought is not taking place, particularly in the south-central part of the study area. These areas contained the highest human and livestock population densities. The local people acknowledged facing increasing resource depletion and indicated drought as the main cause. Pressures on available resources, particularly during drought periods, appeared to have impeded the regenerative capacity of the natural vegetation cover, thereby inducing land degradation. This situation may not easily be rectified because of widespread poverty and inappropriate local perceptions of the solutions. Both of these hinder the adoption of sustainable land management.     

Smoldering Combustion (STAR) for the Treatment of Contaminated Soils: Examining Limitations and Defining Success

Smoldering combustion, commercially available as the Self‐sustaining Treatment for Active Remediation (STAR) technology, is an innovative technique that has shown promise for the remediation of contaminant source zones. Smoldering combustion is an exothermic reaction (net energy producing) converting carbon compounds and an oxidant (e.g., oxygen in air) to carbon dioxide, water, and energy. Thus, following ignition, the smoldering combustion reaction can continue in a self‐sustaining manner (i.e., no external energy or added fuel input following ignition) as the heat generated by the reacting contaminants is used to preheat and initiate combustion of contaminants in adjacent areas, propagating a combustion front through the contaminated zone provided a sufficient flux of air is supplied. The STAR technology has applicability across a wide‐range of hydrocarbons in a variety of hydrogeologic settings; however, there are limitations to its use. Impacted soils must be permeable enough to allow a sufficient flux of air to the combustion front and there exists a minimum required concentration of contaminants such that the soils contain sufficient fuel for the reaction to proceed in a self‐sustaining manner. Further limitations, as well as lessons learned and methods to mitigate these limitations, are presented through a series of case studies. In summary, the successful implementation of STAR will result in >99 percent reduction in contaminant concentrations in treated areas, limited residual contaminant mass, reduced groundwater contaminant mass flux which can be addressed through monitored natural attenuation; and an enhanced site exit strategy, reduced lifecycle costs, and reduced risk. ©2016 Wiley Periodicals, Inc.     

Spring bloom sedimentation in a subarctic ecosystem

A 5-yr study (1985 to 1989) of spring bloom sedimentation in Auke Bay, Alaska, indicates that the sinking response of diatoms to ambient nutrients influences both species succession during the spring bloom and the subsequent sedimentation of new production. Diatoms from the genera Thalassiosira, Chaetoceros and Skeletonema formed the bulk of the spring bloom each year. Growth of Thalassiosira spp. consistently initiated the primary bloom, while Skeletonema costatum tended to grow later in, or after, the primary bloom. We postulate that this successional pattern is driven by interspecific nutrient competition. Overall, sedimentation flux of the dominant species of bloom diatoms was correlated with surface concentrations of cells integrated over the bloom period. In fact, different linear relationships existed when Thalassiosira and Chaetoceros spp. were considered separately, but not for Skeletonema sp., indicating that marked differences exist between the sedimentation tendencies of these genera. The observed inter-generic differences are explicable by the different overall sinking rates, as well as different nutrient-sensitivities of the sinking rates of each genus. Thalassiosira spp., the fastestsinking and most nutrient-sensitive species, contributed up to 10 x more carbon to the benthos in all years of the study, reaching a maximum of 11.1 gCm^-2 over a single spring bloom event in 1988. This study indicates that the tendency to sink to the benthos during and/or after a bloom is highly dependent on species-specific cell physiology, and supports the idea that it is the fast-sinking, nutrient-sensitive diatoms, such as Thalassiosira species, that constitute the major source of vertical carbon flux in this embayment and other such coastal ecosystems during the spring bloom.     

Clostridia dominate 16S rRNA gene libraries prepared from the hindgut of temperate marine herbivorous fishes

Bacterial diversity in the microbial communities of posterior gut sections of three temperate marine herbivorous fish species from New Zealand was characterised using Amplified Ribosomal DNA Restriction Analysis, and 16S rRNA gene amplification and sequencing methods. The fish were collected in 1999–2000 in the Hauraki Gulf, New Zealand (35°54’–36°24’S, 174°48’–175°25’E). The gastrointestinal bacterial communities of Kyphosus sydneyanus (Günther, 1886) (F. Kyphosidae), Odax pullus (Forster in Bloch and Schneider, 1801) (F. Labridae) and Aplodactylus arctidens Richardson, 1839 (F. Aplodactylidae) were dominated by five clades of bacteria, four of which belong to recognized clostridial clusters. The clone libraries of K. sydneyanus and O. pullus contained sequences from most of these clades, but were dominated by members of clostridial clusters XI and XIVa, respectively. The clone library of A. arctidens was dominated by members of clostridial cluster XIVb and an unassigned cluster containing Eubacterium desmolans and Papillibacter cinnaminovorans. The finding that strains of Firmicutes dominated the gastrointestinal microbial communities of all three fish species is consistent with the results of similar studies on terrestrial vertebrate herbivores. This work thus contributes to the view that gastrointestinal symbionts in some marine herbivorous fishes may play a similar role to those in terrestrial vertebrate herbivores studied to date.     

Differences in sensory ecology contribute to resource partitioning in the bats Myotis bechsteinii and Myotis nattereri (Chiroptera: Vespertilionidae)

Coexisting animal species frequently differ in resource use in at least one niche dimension and thus avoid competition. While a range of morphological differences that lead to differentiation in animals' mechanical access to food have been identified, the role of sensory differences in within-guild niche differentiation has received less attention. We tested the hypothesis that differences in sensory access to prey contribute to resource partitioning between potentially competing species using two sympatric, similar-sized, congeneric bat species as a model system. Nursery colonies of Natterer's bat (Myotis nattereri) and Bechstein's bat (Myotis bechsteinii) roost in bat boxes in the same orchard and forage in forests and orchards nearby. In observations and behavioural experiments with freshly captured M. bechsteinii, we showed that individuals are able to hunt using prey-generated sound alone. In contrast, M. nattereri rarely uses prey-generated sound, but instead is able to find prey by echolocation very close to vegetation. In accordance with these behavioural data, we showed that M. bechsteinii has significantly larger ears than M. nattereri, providing it with superior detection and localization abilities for relatively low-frequency prey rustling sounds. We hypothesized that these differences in sensory ecology of the two syntopic, congeneric species would contribute to resource partitioning, so that M. bechsteinii would find more noisy prey taxa, possibly hidden in vegetation, by listening for prey sounds, while M. nattereri would have better access to still prey using echolocation or associative learning. Analysis of faecal samples collected on the same nights from bat boxes occupied by each species corroborated this prediction. The diets of the two species differed significantly, reflecting their different prey perception techniques and thereby supporting the hypothesis that differences in sensory ecology contribute to niche differentiation. Electronic supplementary material Supplementary material is available for this article at and accessible for authorised users. B.M. Siemers and S.M. Swift contributed equally to this work.     

Fertilization in natural populations of the dioecious brown alga Fucus ceranoides and the importance of the polyspermy block

The brown alga Fucus ceranoides L. was studied in several estuaries on the Isle of Man (Great Britain) in the summers of 1989 and 1990. The objective were to determine the success of natural fertilization in a dioecious organism with external fertilization and to contribute to our understanding of processes such as polyspermy blocks and propagule settlement under natural conditions. Gamete release occurred on a semilunar cycle near full and new moons; at such times, settlement densities of 500 zygotes cm^-2 d^-1 were common. Gamete release was largely restricted to daytime high tides. Fertilization success was high: about 95 to 100% of all eggs released were fertilized, and 1 to 9% of these zygotes were polyspermic. The incidence of polyspermy increased towards the upper limit of F. ceranoides in the estuary of the river Neb; this may be significant in the context of the Na⁺-dependent block against polyspermy. Levels of polyspermy were not related to fertilization success (R²=0.06). Rates of pronuclear migration and karyogamy determined in the laboratory were used as an internal clock to estimate when eggs were fertilized in the field. Most eggs were fertilized 30 to 120 min after plants were immersed by the incoming tide, which corresponded to the period 60 min before to 30 min after high tide. The high success of fertilization suggests that polyspermy blocks are important in nature, and, in combination with the high settlement of zygotes, shows that population size in F. ceranoides is determined by post-settlement mortality, not by propagule availability.     

The spatiotemporal expression pattern of trypsinogen and bile salt-activated lipase during the larval development of red porgy (<Emphasis Type="Italic">Pagrus pagrus</Emphasis>, Pisces,Sparidae)

A restoration programme was introduced in the Mondego Estuary (Portugal) to recover seagrass beds of Zostera noltii endangered by eutrophication. A long-term survey of 10 years was used to assess the development of the processes involved, focusing one of the key species (Cyathura carinata, Isopoda). The mitigation measures implemented since 1998 (nutrient loading reduction, freshwater circulation improvement and seagrass bed protection) enhanced water quality and seagrass recovery, thus preventing the development of macroalgal blooms. C. carinata was resilient to the occurrence of floods and macroalgal blooms, although both events caused dispersion of individuals. This isopod was not much influenced by the changes occurring in the estuary, showing an unalterable population structure during the entire study period. After 1998, its density and biomass became more stable at an inner unvegetated sand flat area, where this isopod was most abundant; its population slightly increased in a bare mud flat at the middle section of the estuary; but it could not establish successfully in a downstream Z. noltii bed, contrarily to other common estuarine species. Apart from other unknown reasons, the disrupted balanced between trematodes and their hosts, caused by the eutrophication processes, may have an important role in the discontinuity of C. carinata at the Z. noltii bed. If the intertidal areas become fully restored to the original seagrass coverage, high prevalence and intensity trematodes may prevent this isopod and other crustaceans from recovering within the intervened areas, by enhancing host mortality and recruitment failure. In order to avoid this kind of situation, it may be necessary to survey the levels of parasite infestation within the target hosts and safeguard areas where crustaceans present healthy populations.