The occurrence and significance of Cladocera (Crustacea) in some streams of Central Indiana,U.S.A.

Although Cladocera are collected often in large rivers, their importance in streams has been under-estimated. This paper summarizes the results of a preliminary study of the benthic Cladocera in the streams of three watersheds in South Central Indiana. Seventeen sites were sampled with respect to species of benthic Cladocera present, their relative abundance, population size, and population dynamics.Cladocera were present in all streams and sites in the three watersheds. Nineteen species were collected: 13 species from the family Chydoridae, 3 Daphniidae, 2 Macrothricidae, and 1 Bosminidae. Just four species — Alona circumfimbriata, Chydorus brevilabris, Pleuroxus denticulatus, and Macrothrix laticornis — made up 68–96% of the numbers at all sites.Density of Cladocera ranged from 3–5200 m^–2 and they reproduced and maintained populations in the streams sampled. Numbers were generally high in October and early November and decreased to near zero in late December and January. The most important factor appearing to affect population sizes was discharge. Numbers at almost all sites decreased significantly after a rainfall increased discharge.A Principal Components and clustering analysis grouped sites with similar physical parameters in a continuum of low to high order. Sites with low numbers of Cladocera were generally shallow, narrow, and had a loose unconsolidated substrate. Sites with high population numbers were generally deep, wide, and had a stable substrate that accumulated detritus.     

Spatial and temporal variation of photosynthesis in intertidal Mazzaella laminarioides (Bory)Fredericq (Rhodophyta, Gigartinales)

The red alga Mazzaella laminarioides is an economically important species with an extended latitudinal distribution along the Chilean coast. Its populations form mid-intertidal stands, several meters wide, and therefore are differentially exposed to environmental variables that result in temporal and spatial variability in productivity. We evaluated the effect of latitude and intertidal height on productivity by in situ measurement of photosynthetic performance. Daily and seasonal variations of O₂-evolution rate and maximal quantum yield (F _v/F _m) were determined in plants from the upper and lower intertidal zone at two localities 1500,km apart. Results suggest that plant responses were mainly affected by irradiation, temperature and desiccation. At local level, upper intertidal plants showed a reduced photosynthetic rate and quantum efficiency as compared to those displayed by plants from the lower intertidal, indicating their higher level of excitation energy acclimation. Stronger acclimation differences between upper and lower intertidal plants were observed in spring and summer. Differences in photosynthetic parameters between reproductive phases were recorded in autumn and winter, regardless of the position of the individuals in the intertidal zone. The effects of tidal elevation on seasonal patterns of photosynthesis were also influenced by latitude. Seasonal variation in photosynthetic efficiency was observed in plants from the northern population at both intertidal elevations, but only at the upper intertidal level in the southern population. This study shows that production variability in M. laminarioides results from differences in the intensity of environmental factors observed seasonally at local (intertidal) and latitudinal scales.     

Culture of Gigartina Skottsbergii (Rhodophyta) in Southern Chile. A Pilot Scale Approach

In the last 10 years studies on the management and exploitation of Chilean carrageenophytes have proliferated in response to the increasing development of the local processing industry. One of the most important sources of raw material for Chilean carrageenan, Gigartina skottsbergii Setchell et Gardner, was the subject of an intensive study to design a commercial cultivation technique which could be an alternative to wild harvest. In this context this pilot study reports the first successful attempt to culture G. skottsbergii from spores to harvestable plants. A three-step farming approach was developed: (i) seeding of spores onto scallop shells followed by a two-month nursery period in a greenhouse (until the development of initial upright thalli from the discoid crust occurred), (ii) outplanting juvenile plants on shells in the sea on a long-line system (until thalli attained 3–4 cm diameter) and (iii) detachment of fronds from the shells, fixing of individuals to vertical ropes and growth until commercial size was reached. Additional experiments to compare bottom and suspended growth, cultivation by fragmentation and whole fronds and meristematic activity of different zones of the fronds were performed. This study shows the technical feasibility of culturing G. skottsbergii from spores, complemented with growth of vegetative fragments, in order to optimize the management of the culture. In the future, therefore, it may be possible to replace the heavy exploitation of wild beds in southern Chile with farming activities.     

Ceramialean epiphytism in an intertidal Gracilaria chilensis (Rhodophyta) bed in southern Chile

The cultivation of the agarophytic red alga Gracilaria has become an activity of major importance in several parts of the world. However, Gracilaria cultivation in Chile still faces problems such as epiphytism. We report ceramialean epiphytism abundance, recruitment patterns and the microscopic stages fixed on the Gracilaria thalli in an intertidal bed (Metri bay) of southern Chile. Using a factorial field experiment, we analyze the effect of intertidal elevation and the use of epiphyte free inoculum on the abundance of ceramialean epiphytic algae. This evidence is used to provide management and control recommendations for ceramialean epiphytes. The results show a summer recruitment and increase in abundance of ceramialean epiphytes. A seasonal and spatial pattern of abundance of microscopic stages of this epiphytic algae was also found, showing a significant increase from the apical (new tissues) to the central parts of the thalli (older tissues). Apical tissues are free of epiphytic propagules. The epiphyte-free tissue zone decreases significantly from winter to summer. Also, a significantly higher density of microscopic stages of ceramialean epiphytes was found on the thalli collected in the farming are a during the summer at low tidal levels. The experimental results indicated that the abundance of epiphytes was greater at the lower tidal levels than at the higher distribution limits of Gracilaria and it was not possible to control epiphytism by manual cleaning. This revised version was published online in September 2006 with corrections to the Cover Date.     

Phenology of Gigartina skottsbergii (Gigartinaceae,Rhodophyta) in Ancud Bay,southern Chile

This study reports the variations in biomass and reproductive phenology in a natural bed of Gigartina skottsbergii over a period of a year and correlates these variations with the abiotic factors solar radiation, number of daylight hours, water temperature and salinity. The results obtained show an annual production cycle with maximum biomass values in spring-summer, correlated with high solar radiation and to a lesser extent with salinity. Sexual reproduction was maximum in autumn-winter, correlated with low temperature and short-day conditions. The population showed a large gametophytic dominance according to size and biomass, which suggests that there is not ecological equivalence between the life history phases of the species. Finally, based on the results, a restriction of harvesting to spring-summer is suggested.     

Comparison of five cladoceran species in short- and long-term copper exposure

The study was carried out to assess the effect of both short-and long-term copper exposure on five cladoceran species differing in body size and habitat, i.e. Daphnia magna, D. pulex, D. galeata, Bosmina longirostris, and Chydorus sphaericus. The species-specific 48 h EC₅₀ values for fed neonates were used to determine the chronic exposure levels (52% and 65% of the EC₅₀ values). The experiment was run at two food levels. Long-term copper exposure retarded growth in each of the species studied. However, the copper treatments did not affect the clutch sizes of the experimental animals. At a low food level, copper exposure increased mortality in every species studied. The intrinsic rate of increase, r, was reduced in the copper-exposed populations. The sensitivity to copper was higher in the small lake species, compared to D. magna and D. pulex that are commonly used in standard toxicity tests. Of the species studied, B. longirostris had the highest sensitivity to both acute and chronic copper stress. The different sensitivities of the species studied are discussed in an ecological context.     

Geographical and experimental assessment of the distribution ofGracilaria species (Rhodophyta: Gigartinales) in relation to temperature

Tolerance and growth at temperatures from 0° to 36°C were investigated using 15 species and strains ofGracilaria Grev. isolated from tropical and temperate coasts of the Atlantic and eastern Pacific Oceans. All survived a minimum of 15°C and, with two exceptions, a maximum of 28°C. Only two species tolerated 34°C and none 36°C which was rapidly lethal. Isolates intolerant of temperatures less than 15°C were generally species known only from tropical waters, whereas species isolated from temperate waters tended to be eurythermal, and most seemed not to be restricted to cooler waters. Maximum growth of warm-water isolates tended to occur over a broad range of warmer temperatures, 20°C and higher, and usually extended to the upper limits of thermal tolerance. Isolates from temperate waters showed maximum growth at 20° or 15°C, and there was no appreciable growth of any of the isolates below 10°C. These experimental results are in accord with known distributional patterns ofGracilaria. There is a correlation between temperature and number of species, with most species reported from warm-water areas where the mean water temperature is 25°C or more. Where the 3-month mean minimum temperature is less than 20°C, there is a rapid decline in number of species. In the eastern Atlantic, the relationship is less obvious as few species have been reported from the warm-water region. This is quite likely the result of other environmental factors.NRCC No. 23817Paper presented at the Seaweed Biogeography Workshop of the International Working Group on Seaweed Biogeography, held from 3–7 April 1984 at the Department of Marine Biology, Rijksuniversiteit Groningen (The Netherlands). Convenor: C. van den Hoek.     

Woody species colonisation in relation to habitat productivity

A study was conducted to analyse the effect of habitat productivity on woody species colonisation. Three soil types were distinguished: a relatively poor sandy soil type (1), a somewhat richer sandy type (2) and a relatively rich sandy loamy type (3). Chronosequences were established on these three soil types of 38 (type 1), 20 (type 2) and 54 years (type 3) after abandonment. In total 117 vegetation relevées were used to analyse life form change and species responses during old field succession via regression models. On the rich soil type the colonisation rate of woody species was slower than on the poor soil type. This can be explained by higher abundances of perennial species during the first 20 years after abandonment on the rich soil type in contrast to the poor soil type. Perennial species may delay the woody species colonisation. First they close the bare ground which inhibits germination and next they compete with woody seedlings for light, water and nutrients. The effect of habitat productivity on woody species colonisation can only be determined appropriately by taking life history traits into account. Early successional 'pioneer' woody species dispersed by wind have less difficulties colonising old fields than late successional 'forest' species; they colonise old fields prior to the development of a dense perennial sward. Forest species depend on animals to be dispersed which are attracted by vegetation structure. In ± 30 years on the poor soil type and in ± 45 years on the rich soil type woody species become dominant relative to other life forms. Forest species like Quercus robur L. invaded relatively early (<5 years) in contrast to other studies which probably coincides with the distance to seed sources (forest edges).     

Cultivation of Gigartina skottsbergii (Gigartinales, Rhodophyta): Recent advances and challenges for the future

This study integrates landings statistics and biological studies of the red algaGigartina skottsbergii Setchell & Gardner. The analysis of the landings and carrageenan production in Chile suggeststhat this resource will suffer a strong harvesting pressure during the nextyears. Biological results on sporulation, germination, sporeling growth and survivorship in laboratory,indoor tanks and field conditions, indicated that cultivation of this species istechnically feasible, as spores can be seeded on ropes and other substrata. Vegetative propagation of this species through tissue fragmentationis also possible. Vegetative fragments of this carrageenophyte have 20 to30% higher growth rates than whole fronds in suspended culture systems. Protoplast production can be also explored for bypassing restrictions inspore availability. Major advantages that encourage the cultivation of G. skottsbergii include its gel quantity and quality, its pathogen-freecondition, a high reproduction potential and its regeneration capacity. Onthe other hand, the major constraints are related to its relatively slowgrowth as compared to other carrageenophytes, limited availability ofspores and high mortality during juvenile stages.     

Healing and regeneration responses in Gigartina skottsbergii (Rhodophyta, Gigartinales): optimization of vegetative propagation for cultivation

The red alga Gigartina skottsbergii is becoming increasingly valuable as a resource to providing the raw material for the carrageenan industry established in Chile and elsewhere. As a result, wild stocks of the species are subject to intense harvesting by local fishermen. With the current levels of harvesting, it seems likely that natural stands of G. skottsbergii will soon collapse. Although cultivation seems an alternative, knowledge regarding the biology of the species is exceedingly limited. This study reports the first attempt to determine the optimal conditions for vegetative propagation of this species in the laboratory. For this purpose, the processes of wound healing and regeneration of frond fragments and haptera were studied under controlled conditions of temperature, light, and media strength. Our results demonstrated that excised tissues of G. skottsbergii were able to seal the exposed areas in approximately 20 days, by a wound healing process characterized by a re-differentiation of medullary cells into a normal cortex. Our data also demonstrated that frond fragments are better than haptera for propagation purposes. The development of new cortical tissue at the cut surface is followed, within 60 days, by localized blade-like outgrowths along the repaired area. Furthermore, the healing and regenerative responses in both frond fragments and haptera differed in efficiency according to the various combinations of factors, with optimum of 10–15 °C, 5 ?mol m^?2 s^?1 and plain seawater or standard SFC medium for the fronds. The two types of responses were negatively affected by seawater enriched with a double concentration of nutrients.     

Microgeographic variation in allozyme frequencies in relation to the degree of exposure to wave action in the dogwhelk Nucella lapillus (L.) (Prosobranchia: Muricacea)

Nucella lapillus from 15 sites 50 m to 21 km apart in S. Devon, S. W. England were analysed for allozyme variation at eight soluble enzyme loci. Sites were classified as either Exposed or Sheltered and a hierarchical analysis of allozyme variation carried out using Wright's Fixation Index, F_ST. Whelks from Sheltered sites segregated for alleles at the Est-3, Lap-2, Pep-2 and Mdh-1 loci which were virtually absent from exposed sites resulting in high F_ST values (0.289–0.506) when all samples were included. Consequently mean heterozygosity of the Sheltered samples was roughly twice that of the Exposed. Between Sheltered sites the frequencies of these 'additional' alleles varied substantially, even on a microgeographic scale and were found to be highly correlated with exposure. Within individuals the presence of the 'sheltered' alleles was correlated with the possession of the 'sheltered' shell shape as indicated by length divided by aperture height. This must necessarily be the case, however, if both are related independently to exposure. Although these correlations imply the action of selection there is evidence within the data for stochastic factors affecting the pattern observed. Complicating the picture further is the correspondence observed in the distribution of the 'sheltered' alleles with the known distribution of chromosomal translocations. Phenotypic associations within individuals also support the hypothesis that variation at the Est-3, Lap-2, Mdh-1 and Pet-2 loci is related to variation in chromosome number. However, the nature of the relations of karyotype and allozyme variation with shell shape and exposure remain speculative.     

New insights into the biodiversity and generic relationships of foliose Bangiales (Rhodophyta) in Iceland and the Faroe Islands

Foliose species of the Bangiales (Porphyra sensu lato) have a long history of study in the N Atlantic, but there are still regions, especially in the northern parts of the N Atlantic that need more attention. A molecular study using rbcL and cox1 sequences was undertaken to assess the diversity of foliose Bangiales species in Iceland and the Faroe Islands. Herbarium collections from the intertidal and subtidal of Iceland (summer and winter) and the Faroe Islands (all seasons) revealed a total of 13 species (11 common to both areas), which were referred to four of the genera recognized in a recent two-gene global phylogeny. Boreophyllum birdiae, Porphyra dioica, P. linearis, P. purpurea, P. umbilicalis, Pyropia ‘leucosticta’ A, Pyropia njordii Mols-Mortensen, J. Brodie & Neefus, sp. nov., Wildemania amplissima and W. miniata were common to both areas, while Pyropia thulaea and Wildemania abyssicola (Kjellman) A. Mols-Mortensen & J. Brodie, comb. nov. (=Porphyra abyssicola Kjellman) were reported from Iceland but not from the Faroe Islands; Porphyra sp. FO and Pyropia elongata were reported from the Faroe Islands but not from Iceland. Boreophyllum birdiae is reported for the first time for Iceland and Porphyra sp. FO is reported for the first time for the Faroe Islands. Pyropia njordii is described from the Faroe Islands and is also recorded for Iceland, Greenland, New England, USA and Nova Scotia, Canada. A total of 25 foliose Bangiales species are now reported from the N Atlantic and these results demonstrate the importance of investigating as many areas as possible to reach a more complete understanding of species diversity and distribution.     

Random amplified polymorphic DNA (RAPD) identification of genetic variation in three species ofPorphyra (Bangiales,Rhodophyta)

The random amplified polymorphic DNA (RAPD) technique was used to characterize three species ofPorphyra from the western North Atlantic and adjacent Gulf of Mexico. Twenty 10-mer primers were screened for DNA amplification usingPorphyra template DNA. Nine of these oligonucleotide primers, all (G+C)-rich, were positive or band-producing, but yielded poor or variable band resolution. Subsequent use of the universal 20-mer M 13 primer resulted in both clear band resolution with a minimum of secondary bands and a high degree of reproducibility. Amplification products for DNA from six regional isolates ofPorphyra carolinensis Coll et Cox,P. leucosticta Thuret in Le Jolis andP. rosengurttii Coll et Cox were compared to each other and toBangia atropurpurea (Roth) C. Agardh. Results provide evidence of both genetically hetero- and homogeneous populations. Use of the RAPD method with the M 13 primer yields amplification products which can be used to fingerprint specific genotypes. This procedure could be used to discriminate between hetero- and homokaryotic fusion products from previously characterized donor strains.     

Causes and implications of intra-clonal variation in Gracilaria chilensis (Rhodophyta)

Strain selection studies in Gracilaria chilensis detected significant levels of intra-clonal variation. These findings motivated more detailed studies on the causes and implications of intra-clonal variation in these and other red algal species. Our results indicate that intra-clonal variation is common among replicated units (e.g.: carpospores and ramets) of several red algal species and suggest that a larger data base probably will show the occurrence of various kinds of intra-clonal changes, differing in frequency of occurrence and magnitude of phenotypic expression. It is likely also that different species would exhibit different amounts of variation. Four types of factors may cause intra-clonal variation: (1) physiological or developmental differences among ramets, (2) localized pathogen infections, (3) several kinds of genetic changes, and (4) sporeling coalescence. Intra-clonal variation among ramets: (1) increases the possibility of genet survival, (2) explains the origin of morphological and physiological differences among ramets of a given genet, (3) explains the large population variation found in many clonal species and (4) suggests that strain selection of some economically important seaweeds should be thought of as a fairly continuous process due to the instability of some of these clones.     

Daylength and development in four species of Ceramiaceae (Rhodophyta)

Developmental patterns in four species of Ceramiaceae were determined using excised thallus apices grown under a range of light periods. Models of thallus development and organization based on these patterns are presented. Increased rates of apical cell division, greater growth of apical fragments and increased average cell size were found with increasing number of hours light per day between 8–16 and 16–8 h. No aspect of growth investigated was associated with photoperiodic phenomena, and growth occuring during the light break (8-7.5-1-7.5 h) was intermediate between that in 8–16 and 12–12 h. Three patterns of cell elongation were found in the four species in which (1) cell age, (2) cell age and position and (3) cell age, cell position and light period determined cell length at different axial cell positions. Elongation was followed within cells, along axes ofAntithamnion spirographidis for plants grown under different day lengths. Three regions of development were found along main axes: (1) an apical region in which basipetal expansion was greater than acropetal expansion. (2) a zone of stability with equal elongation in apical and basal growth region of cells, and (3) a basal region with greater acropetal expansion. With increasing daylength, the zone of stability was extended to greater ranges of cell length.     

Inter- and intrapopulation genetic variation in species ofPorphyra (Rhodophyta: Bangiales) from British Columbia and adjacent waters

Starch gel electrophoresis of 17 proteins has provided data on inter- and intrapopulation genetic variation in 20 species ofPorphyra occurring in British Columbia and adjacent areas.P. cuneiformis andP. nereocystis showed no within species variation, even over ranges of more than 1000 km. Populations ofP. abbottae, P. fallax, P. fucicola, P. gardneri andP. schizophylla were characterized by fixation for certain alleles. The number of polymorphic loci in a population ranged from zero to nine, depending on the species. Six species had populations that were polymorphic at just a single locus. Only two species (P. mumfordii andP. pseudolanceolata) had populations that were polymorphic at more than three loci. These levels of genetic variation are lower than those reported for populations of JapanesePorphyra species. Eleven taxa were polymorphic for 6-phosphogluconate dehydrogenase, the most variable enzyme. No within species polymorphisms were detected for bromoperoxidase, lactate dehydrogenase, superoxide dismutase or phycoerythrin. Possible evidence for the chimeric nature of the thallus was observed only inP. mumfordii.     

Growth and survival performance of the gametophyte of Gigartina skottsbergii (Rhodophyta, Gigartinales) under defined nutrient conditions in laboratory culture

Gigartina skottsbergii is a commercially important carrageenan producer that has been suffering severe extraction pressure in Chile’s Magellan Region and Cape Horn Archipelago since 1998. In order to create baseline information for its cultivation and repopulation, we studied the effects of agricultural fertilizers on growth of G. skottsbergii early developmental stages. The culture media utilized were: a) seawater + Bayfoland, b) seawater + Superphosphate, c) seawater + Urea, d) seawater + Provasoli and e) seawater as a control. The culture conditions were: a) 12L:12D photoperiod; b) temperature 8 ± 1°C and c) irradiance at 45 μmol photons m⁻² s⁻¹. After 60 days, higher relative growth rates between treatments were observed; the treatments that included Bayfoland and Provasoli showed greater growth (382 ± 55 and 378 ± 50 μm, respectively,) compared to Superphosphate (88 ± 16 μm), control (78 ± 10 μm) and Urea (70 ± 11 μm) treatments, after 81 days. The Urea treatment and the control had inhibitory effects on G. skottsbergii germlings growth and survival, as evidenced by progressive loss of pigmentation and death after 60 days. These results showed that Bayfoland was an excellent alternative to develop cultures.     

Interannual variation of the abundance of Mazzaella cornucopiae (Rhodophyta, Gigartinales) from Pacific Canada in relation to changes in abiotic variables

The seaweed Mazzaella cornucopiae (Postels & Ruprecht)Hommersand is common in rocky intertidal areas from Pacific Canada andis a potential economic resource. In both 1993 and 1994, the abundanceof M. cornucopiae from Prasiola Point, southern Barkley Sound, washigh in spring and summer and low in fall and winter. In 1995, however,the abundance in summer was unexpectedly low, and this trend deepenedin 1996. Correlations between the temporal changes of abundance and ofsome abiotic variables were done as a first approach to explaining thesechanges of abundance. The abiotic variables used were air temperature,sea surface temperature, wave height, all three measured on an oceanicbuoy close to Prasiola Point, and seawater salinity, determined for coastalwaters from northern Barkley Sound. These were the closest sites toPrasiola Point for which reliable abiotic data existed. None of thecorrelations were significant. Field observations done at Prasiola Pointsuggest that air temperatures reached higher values there than at theoceanic buoy. Together with irradiance, in situ air temperature may havehad an important role in the interannual differences of abundance througha higher physical stress on thalli, resulting in the high proportion ofbleached tissues observed in summer 1996. Future studies on thepopulation dynamics of M. cornucopiae should benefit fromquantifying these variables in situ.