Strontium:cakium concentration ratios in otoliths of herring larvae as indicators of environmental histories

Synopsis Elemental analyses, using wave-length dispersive electron microprobe techniques on otoliths from reared Atlantic herring larvae, Clupea harengus, showed trace quantities of strontium relative to that of calcium, and an inverse relationship between Sr/Ca concentration ratios and rearing temperature. These data are consistent with those for coral aragonite, in that there appears to be an inverse temperature effect on physiological incorporation of strontium in the otolith aragonite. Our determinations of Sr/Ca concentration ratios of lab-reared herring larvae showed that the deposition of strontium relative to calcium and the rearing temperature were related, where: T (° C) = −2.955 [Sr/Ca] × 1000 ± 19.172. This principle thus makes it possible to use Sr/Ca concentration ratios in fish otoliths to delineate past temperatures experienced by an individual. Further, combining electron microprobe analyses with scanning electron microscope (SEM) examinations of daily increments in the same otolith makes it possible to reconstruct the temperature history for an individual fish on a time scale of days. An example of the application of the technique to an approximately six-month-old field-caught herring larva is given, and the limitations of the technique are discussed.     

Lysosomal perturbations in fish liver as indicators for toxic effects of environmental pollution

• 1.1. Lysomones play a key role in liver injury in fish caused by organic and inorganic xenobiotics. The lysosomal stability test was transferred to fish liver with the aim of testing responsive and practicable methods for biological-effects monitoring.
• 2.2. A two-step response of lysosomes in fish liver could be discerned, reflected by the activity (number and size of lysosomes) and the injury (membrane destabilisation) of the lysosomal detoxifying system.
• 3.3. Significant differences, with respect to lysosomal enlargement, membrane stability and pathological lipid accumulation, were found along a pollution gradient throughout the year.
• 4.4. The lysosomal tests clearly reflect the breakdown of the adaptive capacity of the fish liver to toxic injury. Therefore, a test battery measuring lysosomal perturbations should be recommended for the biological-effects monitoring.

     

Lysosomal perturbations in fish liver as indicators for toxic effects of environmental pollution.

1. Lysomones play a key role in liver injury in fish caused by organic and inorganic xenobiotics. The lysosomal stability test was transferred to fish liver with the aim of testing responsive and practicable methods for biological-effects monitoring. 2. A two-step response of lysosomes in fish liver could be discerned, reflected by the activity (number and size of lysosomes) and the injury (membrane destabilisation) of the lysosomal detoxifying system. 3. Significant differences, with respect to lysosomal enlargement, membrane stability and pathological lipid accumulation, were found along a pollution gradient throughout the year. 4. The lysosomal tests clearly reflect the breakdown of the adaptive capacity of the fish liver to toxic injury. Therefore, a test battery measuring lysosomal perturbations should be recommended for the biological-effects monitoring.     

Toxic metals in freshwater fish from the Zagreb area as indicators of environmental pollution

The aim of this investigation was to determine the levels of heavy metals and metalloids in freshwater fish from the Zagreb area. A total of 216 freshwater fish samples from 5 sites were examined: Sava river upstream from Zagreb, Sava river at Zagreb, Sava river downstream from Zagreb, Jarun Lake, and 5 "ecologic" fishponds from the Zagreb surroundings. The metals lead, cadmium, mercury and the metalloid arsenic were determined by the method of atomic absorption spectrometry. The mean pooled levels of lead, cadmium and arsenic in all fish samples were 112.3 +/- 95 micrograms/kg, 8.5 +/- 11 micrograms/kg and 23.5 +/- 36 micrograms/kg, and did not exceed the allowed levels of 1,000 mg/kg, 100 micrograms/kg and 200 micrograms/kg, respectively. In 4 fish samples, the levels of mercury exceeded the allowed limit of 500 micrograms/kg (509, 596, 605 and 788 micrograms/kg), however, the pooled mean level of mercury was 127.8 +/- 90 micrograms/kg. There was no major difference in the levels of heavy metals between the two fish families observed, although the levels of lead, cadmium and mercury were higher in the family Ictaluridae (144 vs. 107 micrograms/kg, 10.4 vs. 8.2 micrograms/kg, and 153 vs. 124 micrograms/kg, respectively), whereas the level of arsenic was higher in the family Cyprinidae (23.8 vs. 21.8 micrograms/kg). Although the Sava river at Zagreb is the main recipient of sewage and wastewater in the Republic of Croatia, the levels of heavy metals were within the allowed limits in all groups of freshwater fish samples, with the exception of 4 samples that contained moderately elevated levels of mercury. Study results suggest that only mercury could be considered a good indicator of environmental pollution, because higher levels of mercury were measured in the fish from the Sava river than in the fish from the Jarun Lake and fishponds from the Zagreb surroundings, considering both pooleded and fish family specified data.     

Histological changes in fish hepatopancreas and kidney as indicators of environmental quality in tropical bays

Environmental Biology of Fishes - Biomarkers are used to assess health conditions of organisms and consequently to indicate environmental hazard, being important tools to address the effects of...     

The use of otoliths as indicators of Little Penguin Eudyptula minor diet

The validity of using otoliths from stomach contents quantitatively to determine the number and size of fish consumed was tested on Little Penguins. They were fed different meal sizes of known number and size of fish and the stomach contents were recovered after various time intervals. There were no differences in estimates of original fish size when calculated from otolith length or weight. Rate of digestion of otoliths tended to decrease with increased meal size but increased with time after ingestion. Digestion of otoliths proceeds rapidly and, if ignored, estimates of numbers of fish consumed and of original fish size can be significantly underestimated. This problem can be partially solved by inspection of otolith condition and restricting calculations of fish size to otoliths unaffected by digestion. Many factors introduce variations into rate of otolith degradation and further species-specific studies are required before appropriate correction factors can be applied.     

The use of otoliths as indicators of Little Penguin Eudyptula minor diet

The validity of using otoliths from stomach contents quantitatively to determine the number and size of fish consumed was tested on Little Penguins. They were fed different meal sizes of known number and size of fish and the stomach contents were recovered after various time intervals. There were no differences in estimates of original fish size when calculated from otolith length or weight. Rate of digestion of otoliths tended to decrease with increased meal size but increased with time after ingestion. Digestion of otoliths proceeds rapidly and, if ignored, estimates of numbers of fish consumed and of original fish size can be significantly underestimated. This problem can be partially solved by inspection of otolith condition and restricting calculations of fish size to otoliths unaffected by digestion. Many factors introduce variations into rate of otolith degradation and further species-specific studies are required before appropriate correction factors can be applied.     

Stable lead isotope ratios from distinct anthropogenic sources in fish otoliths: a potential nursery ground stock marker

Variations measured in the lead (Pb) stable isotope ratios in otoliths of juvenile tropical reef fish Scarus perspiculatus, Abudefduf abdominalis and Dascyllus albisella reflect mixing of anthropogenic lead from the Kaneohe Bay watershed and 'background' lead characteristic of the adjacent ocean. The otoliths and water samples collected in a transect across the bay demonstrated nearly identical Pb isotopic trends. The Pb isotopic composition of the watershed has a low 206Pb/204Pb signature primarily reflecting past combustion of tetra-ethyl Pb additive in fuels. Ocean water not contaminated by this watershed signature has a different, high 206Pb/204Pb isotopic composition, similar to previously measured Asian anthropogenic aerosols and natural eolian dusts, where the anthropogenic signal dominates. Where a history of past anthropogenic Pb contamination exists, it may be possible to use the ratios of Pb stable isotopes in fish otoliths to reconstruct the nursery grounds of fish.     

A first attempt at determining larval growth in three Antarctic fish from otoliths and RNA/DNA ratios

Otolith growth and RNA/DNA ratios of larval stages of Notolepis coatsi, Gobionotothen gibberifrons and Trematomus scotti, three Antarctic fish, were studied during early 1998. RNA/DNA ratios were significantly different between the notothenioids and paralepidids (P<0.01), but similar among notothenioids (P>0.05). The ratios were independent of larval total length and water temperature. Recent otolith growth (based on the last five increments) and biochemical indices correlated slightly, but not significantly. N. coatsi inhabited deeper and colder waters of the Weddell Sea and showed less growth than the other species, which are associated with the Antarctic Peninsula. In all three species, some larvae had very good growth rates though most were rather poor. Recent growth indices might allow the detection and back-dating of growth changes in Antarctic larvae, and provide insight into a crucial yet poorly understood life-phase of these fish.     

Aral Sea Ostracoda as environmental indicators

Fluctuations in the level and chemistry during its history have played a major part in shaping the floral and faunal communities of the Aral Sea. Of the eleven species of Ostracoda (Crustacea) known to have been living in the Aral Sea in 1960, only one survives today due to the anthropogenically induced salinity increase of the past three decades. The origins of a mixed fresh- and brackish-water ostracod fauna are discussed, and it is concluded that some of the major faunal elements must have reached the Aral Sea Basin during a past high water level phase when connection existed with the Caspian Sea. The taxonomic position of key taxa is clarified, and the major elements of the pre-1960 Aral Sea ostracod fauna are illustrated from Holocene sequences. Aral Sea, Ostracoda, Holocene, palaeolimnology.     

Algae as indicators of environmental change

Despite an increased awareness by governments and the general public of the need for protecting all types of aquatic habitats, human impacts continue to impair the services that these ecosystems provide. Increased monitoring activities that locus on all major biological compartments are needed to quantify the present condition of Earth's aquatic resources and to evaluate the effectiveness of regulations designed to rehabilitate damaged ecosystems. Algae are an ecologically important group in most aquatic ecosystems but are often ignored as indicators of aquatic ecosystem change. We attribute this situation both to an underappreciation of the utility of algal indicators among non-phycologists and to a lack of standardized methods for monitoring with algae.Because of their nutritional needs and their position at the base of aquatic foodwebs, algal indicators provide relatively unique information concerning ecosystem condition compared with commonly used animal indicators. Algae respond rapidly and predictably to a wide range of pollutants and, thus, provide potentially useful early warning signals of deteriorating conditions and the possible causes. Algal assemblages provide one of the few benchmarks for establishing historical water quality conditions and for characterizing the minimally impacted biological condition of many disturbed ecosystems. Preliminary comparisons suggest that algal indicators are a cost-effective monitoring tool as well.Based on available evidence from field studies, we recommend development of taxonomic indicators based on diatoms (Bacillariophyceae) as a standardized protocol for monitoring ecosystem change. Both population- and community-level indices have inherent strengths, and limitations and information from both levels of biological organization should be utilized in tandem. However, further information concerning species tolerances to a variety of anthropogenic stressors is needed if autecological indices are to be used routinely for monitoring purposes. While functional measures (e.g. productivity) may also prove useful as monitoring tools, further investigation is required to characterize the reliability of alternative methodologies and to assess the consistency of these indicators under varying field conditions.Author for correspondence     

Trangenic fish as models in environmental toxicology

Historically, fish have played significant roles in assessing potential risks associated with exposure to chemical contamination in aquatic environments. Considering the contributions of transgenic rodent models to biomedicine, it is reasoned that the development of transgenic fish could enhance the role of fish in environmental toxicology. Application of transgenic fish in environmental studies remains at an early stage, but recent introduction of new models and methods demonstrates progress. Rapid advances are most evident in the area of in vivo mutagenesis using fish carrying transgenes that serve as recoverable mutational targets. These models highlight many advantages afforded by fish as models and illustrate important issues that apply broadly to transgenic fish in environmental toxicology. Development of fish models carrying identical transgenes to those found in rodents is beneficial and has revealed that numerous aspects of in vivo mutagenesis are similar between the two classes of vertebrates. Researchers have revealed that fish exhibit frequencies of spontaneous mutations similar to rodents and respond to mutagen exposure consistent with known mutagenic mechanisms. Results have demonstrated the feasibility of in vivo mutation analyses using transgenic fish and have illustrated their potential value as a comparative animal model. Challenges to development and application of transgenic fish relate to the needs for improved efficiencies in transgenic technology and in aspects of fish husbandry and use. By taking advantage of the valuable and unique attributes of fish as test organisms, it is anticipated that transgenic fish will make significant contributions to studies of environmentally induced diseases.     

Soil-inhabiting arthropods as indicators of environmental quality

Soil-inhabiting arthropods such as Collembola, Cryptostigmata and termites as indicators of various environmental gradients and air pollution, being considered both as biotic indices and bioassay monitors, are reported and discussed.     

Stable isotope records from otoliths as tracers of fish migration in a mangrove system

The ratios of stable isotopes ¹⁸O:¹⁶O and ¹³C:¹²C were measured in otolith carbon taken from nine species of fishes caught within mangroves and on the reef at Gazi Bay, Kenya. Before analysis, otoliths were divided into 'larval'post-larval' and 'adult' sections using a drill. Fishes were putatively classified as 'mangrove residents'offshore residents' or 'migrants' on the basis of information from the literature, and depending on where they were caught (mangroves only, offshore only or both mangroves and offshore) in the present study. Eight of the species exhibited an increase in otolith ¹³C:¹²C with age, but this was significant only in the two migrant species Lethrinus harak and Lutjanus fulviflammus . There were no consistent patterns in ¹⁸O:¹⁶O with age, or between migrants and non-migrants. These results suggest that comparing absolute values of otolith oxygen and carbon isotope signatures between fish species is not a useful way of determining migration patterns at this site, because of species-specific differences in carbon metabolism and insufficiently steep gradients in temperature and salinity. Changes in carbon isotope signatures between life stages within a species, however, do hold promise as migration tracers.     

The staining of fish otoliths for age determination

Attempts were made to find methods for the staining of fish otoliths which would give results comparable to those of the Christensen burning technique. A variety of different histological stains and otoliths of different species were experimented with. Otoliths of sole, turbot, brill and scad gave best results when sectioned and stained in acidified Neutral Red, whereas those of cod, hake, whiting, plaice and grey mullet showed up the annuli better when dyed in aqueous Aniline Blue or Toluidine Blue and then sectioned. Small, translucent otoliths such as those of pelagic species may be enhanced by staining in Eosin Y.     

Macroinvertebrates as indicators of fish absence in naturally fishless lakes

1. Little is known about native communities in naturally fishless lakes in eastern North America, a region where fish stocking has led to a decline in these habitats. 2. Our study objectives were to: (i) characterise and compare macroinvertebrate communities in fishless lakes found in two biophysical regions of Maine (U.S.A.): kettle lakes in the eastern lowlands and foothills and headwater lakes in the central and western mountains; (ii) identify unique attributes of fishless lake macroinvertebrate communities compared to lakes with fish and (iii) develop a method to efficiently identify fishless lakes when thorough fish surveys are not possible. 3. We quantified macroinvertebrate community structure in the two physiographic fishless lake types (n = 8 kettle lakes; n = 8 headwater lakes) with submerged light traps and sweep nets. We also compared fishless lake macroinvertebrate communities to those in fish‐containing lakes (n = 18) of similar size, location and maximum depth. We used non‐metric multidimensional scaling to assess differences in community structure and t‐tests for taxon‐specific comparisons between lakes. 4. Few differences in macroinvertebrate communities between the two physiographic fishless lake types were apparent. Fishless and fish‐containing lakes had numerous differences in macroinvertebrate community structure, abundance, taxonomic composition and species richness. Fish presence or absence was a stronger determinant of community structure in our study than differences in physical conditions relating to lake origin and physiography. 5. Communities in fishless lakes were more speciose and abundant than in fish‐containing lakes, especially taxa that are large, active and free‐swimming. Families differing in abundance and taxonomic composition included Notonectidae, Corixidae, Gyrinidae, Dytiscidae, Aeshnidae, Libellulidae and Chaoboridae. 6. We identified six taxa unique to fishless lakes that are robust indicators of fish absence: Graphoderus liberus, Hesperocorixa spp., Dineutus spp., Chaoborus americanus, Notonecta insulata and Callicorixa spp. These taxa are collected most effectively with submerged light traps. 7. Naturally fishless lakes warrant conservation, because they provide habitat for a unique suite of organisms that thrive in the absence of fish predation.     

Use of stable isotope ratios of fish larvae as indicators to assess diets and patterns of anthropogenic nitrogen pollution in estuarine ecosystems

A stable isotope study was carried out to investigate the feeding ecology of the common goby Pomatoschistus microps larvae (Krøyer, 1838), and to assess differences in the response of planktonic food web to nutrient enrichment, in two ecosystems from the Southern European coast with different levels of historical pollution (estuaries of the Minho and Lima Rivers). At each estuary and time (July 2012, November 2012, February 2013, and June 2013), the fish larvae of two size classes (class 0: 0–10 mm; class 1: 10–15 mm), particulate organic matter (POM), and pelagic zooplankton were collected. The stable isotope mixing model SIAR revealed that, despite temporal differences in the relative proportion of prey items ingested, in both estuaries P. microps larvae feed on both planktonic-hyperbenthic food sources, predating mainly on copepods (from 34% to 60%), Mysidacea (from 16% to 28%), and brachyuran zoea (from 14% to 29%). Fish larvae size classes did not differ significantly for δ¹⁵N, and exhibited a very narrow range of the δ¹³C signature. Enriched δ¹⁵N values of all biota in the Lima estuary throughout the study period, with a marked nitrogen enrichment in colder months, are indicative of higher anthropogenic inputs of nitrogen (e.g. sewage and industrial discharges, agriculture) into this system. The δ¹⁵N values of fish larvae and other planktonic groups can be a sensitive bioindicator, because they are highly correlated with the nitrogen content of water (ammonium), indicating that this element has transferred through the planktonic food web. Enriched carbon isotope ratios were observed in warmer months, in both estuaries, and the heavier δ¹³C values in Lima are best explained by differences in the degree of marine influence. This research emphasises the utility of stable isotopes in trophic interactions studies, highlighting the relevance of the stable nitrogen isotope of zooplanktonic communities as a reliable bioindicator to detect patterns of anthropogenic nitrogen contamination in estuarine ecosystems.     

Specific polyamine ratios as indicators of Pinus caribaea microshoot rooting phases

Abstract

This study analysed the changes in the endogenous levels of total and individual polyamines (PAs) during the different rooting phases in Pinus caribaea microshoots: induction, induction-initiation and functional root system emergence. The analysis, performed using high-resolution liquid chromatography, demonstrated that during the inductive phase there is a drop in total PA content in all the fractions, with an increase in the degradation product diaminopropane. In the induction-initiation phase PAs are present in all the fractions. The microshoots with root nodules always presented higher Putrescine (Put) levels, whereas those that did not have them had similar spermidine and Put levels, while maintaining elevated spermine levels. The comparative analysis of microshoots with and without a rooting response indicates that high PA levels are maintained when root manifestation does not occur, coinciding with basal callus formation.     

Iodine content of fish otoliths in species found in diverse habitats

Environmental Biology of Fishes - Expansion of aquatic deoxygenation has altered the quality and availability of habitats and worsened body condition for many fish species through past decades....