Cryptic diversity of Ulva (Ulvales,Chlorophyta) in the Great Bay Estuarine System (Atlantic USA): introduced and indigenous distromatic species

Distromatic foliose blades of the algal genus Ulva are notoriously difficult to identify due to their simple morphologies and few diagnostic characteristics that often exhibit intraspecific variation and interspecific overlap. Hence, species differentiation is difficult and diversity estimates are often inaccurate. Two major goals of this study were to assess the diversity of distromatic Ulva spp. in the Great Bay Estuarine System (GBES) of New Hampshire and Maine, USA, and to compare historical and present day records of these species. Molecular analysis (using ITS sequences) of field-collected specimens revealed four distinct taxa: Ulva lactuca, U. rigida, U. compressa, and U. pertusa. Prior to molecular screening, Ulva lactuca was the only distromatic Ulva species reported for the GBES. Ulva pertusa and the foliose form of U. compressa are newly recorded for the Northwest Atlantic, and the range of U. rigida has been extended. Molecular analysis of historical herbarium voucher specimens indicates that U. rigida, U. pertusa, and the foliose form of U. compressa have been present in the GBES since at least 1966, 1967, and 1972, respectively. The distromatic morphotype of U. compressa is found only in low salinity areas, which suggests that salinity may influence its morphological development. Molecular and morphological evaluations are critical if we are to distinguish between cryptic taxa, accurately assess biodiversity, and effectively monitor the spread of non-indigenous macroalgae.     

Foliose Ulva Species Show Considerable Inter‐Specific Genetic Diversity,Low Intra‐Specific Genetic Variation,and the Rare Occurrence of Inter‐Specific Hybrids in the Wild

Foliose Ulva spp. have become increasingly important worldwide for their environmental and financial impacts. A large number of such Ulva species have rapid reproduction and proliferation habits, which explains why they are responsible for Ulva blooms, known as “green tides”, having dramatic negative effects on coastal ecosystems, but also making them attractive for aquaculture applications. Despite the increasing interest in the genus Ulva, particularly on the larger foliose species for aquaculture, their inter‐ and intra‐specific genetic diversity is still poorly described. We compared the cytoplasmic genome (chloroplast and mitochondrion) of 110 strains of large distromatic foliose Ulva from Ireland, Brittany (France), the Netherlands and Portugal. We found six different species, with high levels of inter‐specific genetic diversity, despite highly similar or overlapping morphologies. Genetic variation was as high as 82 SNPs/kb between Ulva pseudorotundata and U. laetevirens, indicating considerable genetic diversity. On the other hand, intra‐specific genetic diversity was relatively low, with only 36 variant sites (0.03 SNPs/kb) in the mitochondrial genome of the 29 Ulva rigida individuals found in this study, despite different geographical origins. The use of next‐generation sequencing allowed for the detection of a single inter‐species hybrid between two genetically closely related species, U. laetevirens, and U. rigida, among the 110 strains analyzed in this study. Altogether, this study represents an important advance in our understanding of Ulva biology and provides genetic information for genomic selection of large foliose strains in aquaculture.     

Seasonal variation of dominant free-floating and attached Ulva species in Rudong coastal area,China

In this paper, species compositions and seasonal variations of attached Ulva species on Porphyra aquaculture rafts and free floating Ulva species at Rudong coastal area, Jiangsu Province of China were investigated during 2010–2011. Based on the sequences analysis of nuclear-encoded ITS (including 5.8S rDNA regions) and 5S rDNA spacer regions, dominant species of both attached and free-floating Ulva samples were identified as Ulva compressa, Ulva linza, Ulva prolifera and Ulva flexuosa. Phylogenetic tree based on sequences of ITS and 5S rDNA spacer regions for attached and free-floating Ulva species was constructed, respectively. Species compositions of the Ulva population attached on aquaculture rafts varied with seasons, and U. prolifera was only found on aquaculture rafts in March 2011 during the 2010–2011 Porphyra yezoensis cultivation season, which had the same sequences of ITS and 5S rDNA spacer regions as that of the dominant species bloomed in the Yellow Sea of China in 2008. Dominant species of the free-floating Ulva population at the early stage of the green tide were U. compressa, U. flexuosa, and U. linza. Free-floating U. prolifera appeared in the middle of May, 2011. ITS sequence similarity rates of U. compressa and U. flexuosa between the attached and free-floating species were 100%. And ITS and 5S rDNA spacer sequences of the attached and the free-floating U. prolifera population also showed no differences. Further study showed that there were two types of free-floating U. prolifera population (Type 5S-A and Type 5S-B) based on 5S rDNA spacer sequences. The present study would provide some useful information for clarifying the outbreak mechanism of green tides occurred in the Yellow Sea, China.     

Growing Ulva (Chlorophyta) in integrated systems as a commercial crop for abalone feed in South Africa: a SWOT analysis

Over 1,000t fresh weight of Ulva was cultivated on South African abalone farms in 2007, primarily for feed, but in one case to allow partial re-circulation by nutrient removal. The potential of this new commercial crop is analysed. Material is collected from natural free-floating populations and at least four species are commonly grown, with different ecophysiological characteristics. A brown epiphyte, Myrionema strangulans, causes a disease of the Ulva, which is currently managed by farmers by re-stocking. The main potential threat is that some farmers are wary of integrated systems, fearing they may promote disease in abalone, although Ulva has been grown in abalone effluent and fed back to the abalone on one farm for 6 years without adverse effects. Opportunities exist for the expansion of Ulva cultivation via further spread of the abalone industry, the inclusion of seaweed raceways in proposed fish-farming activities, or the potential for the inclusion of high quality cultivated Ulva as a constituent in aquafeed. A conservative estimate of production over a full year from these raceway systems was 26.1 g dw m⁻² day⁻¹ (2006) and 19.7 g dw m⁻² day⁻¹ (2007), similar to maximum figures for total annual microalgal biomass production in outdoor systems.     

Genetically distinct Dutch-domesticated Clarias gariepinus used in aquaculture in southern Africa

Clarias gariepinus, a catfish species widely distributed in Africa including South Africa, is naturally absent from the Western Cape and the coastal Eastern Cape provinces. Because of its potential as an aquaculture species it has been widely used in aquaculture ventures in South Africa, specifically a stock known as Dutch catfish, a domesticated strain developed in the Netherlands. Mitochondrial DNA markers indicate that this stock is genetically distinct from the natural populations of C. gariepinus in South Africa. It could potentially pose a threat to South Africa's natural biodiversity if these fish were to escape from aquaculture farms, or was deliberately introduced into inland waters.     

Exhaustive reanalysis of barcode sequences from public repositories highlights ongoing misidentifications and impacts taxa diversity and distribution

Accurate species identification often relies on public repositories to compare the barcode sequences of the investigated individual(s) with taxonomically assigned sequences. However, the accuracy of identifications in public repositories is often questionable, and the names originally given are rarely updated. For instance, species of the Sea Lettuce (Ulva spp.; Ulvophyceae, Ulvales, Ulvaceae) are frequently misidentified in public repositories, including herbaria and gene banks, making species identification based on traditional barcoding unreliable. We DNA barcoded 295 individual distromatic foliose strains of Ulva from the North-East Atlantic for three loci (rbcL, tufA, ITS1). Seven distinct species were found, and we compared our results with all worldwide Ulva spp. sequences present in the NCBI database for the three barcodes rbcL, tufA and the ITS1. Our results demonstrate a large degree of species misidentification, where we estimate that 24%–32% of the entries pertaining to foliose species are misannotated and provide an exhaustive list of NCBI sequences reannotations. An analysis of the global distribution of registered samples from foliose species also indicates possible geographical isolation for some species, and the absence of U. lactuca from Northern Europe. We extended our analytical framework to three other genera, Fucus, Porphyra and Pyropia and also identified erroneously labelled accessions and possibly new synonymies, albeit less than for Ulva spp. Altogether, exhaustive taxonomic clarification by aggregation of a library of barcode sequences highlights misannotations and delivers an improved representation of species diversity and distribution.     

Molecular assessment of Ulva (Ulvales,Chlorophyta) diversity in Vietnam including the new species U. vietnamensis

Species diversity of Ulva in Vietnam was investigated using three commonly used genetic markers, the nuclear encoded rDNA ITS region and the plastid encoded rbcL and tufA genes. Single locus species delimitation methods, complemented with morphological and ecological information resulted in the delimitation of 19 species. This diversity is largely incongruent with the traditional understanding of Ulva diversity in Vietnam. Only four species identified in this study, U. lactuca, U. reticulata, U. spinulosa, and U. flexuosa, have been previously reported, and seven species, U. ohnoi, U. tepida, U. chaugulii, U. kraftiorum, U. meridionalis, U. limnetica, and U. aragoënsis, are recorded for the first time from Vietnam. Seven genetic clusters could not be associated with species names with certainty. A new species, U. vietnamensis, is described from marine to brackish coastal areas from southern Vietnam based on its morphological and molecular distinctiveness from the currently known Ulva species. A comparison with recent molecular-based studies of Ulva diversity showed that species composition in Vietnam is similar to that of adjacent countries, including Japan, China, as well as Australia. Our study emphasizes the importance of molecular data in the assessment of Ulva diversity, and indicates that a lot of diversity may still remain to be discovered, especially in tropical regions.     

Phylogeography of the genus <Emphasis Type="Italic">Ulva</Emphasis> (Ulvophyceae,Chlorophyta), with special reference to the Japanese freshwater and brackish taxa

The nuclear-encoded ITS and associated 5.8S rDNA regions were sequenced for 72 specimens of Ulva collected from 44 rivers across Japan, including U. prolifera Müller from the Shimanto River, Kochi Prefecture, as well as 26 samples originally identified as U. linza L. from 20 coastal marine areas. Sequence data revealed that the samples fall into six distinct clades: the U. flexuosa Wulfen clade (2 samples), the Ulva linza-procera-prolifera (LPP) complex clade (75 samples), Ulva sp. 1 clade (3 samples), Ulva sp. 2 clade (7 samples), Ulva sp. 3 clade (4 samples) and Ulva sp. 4 clade (7 samples). The LPP complex contained a mixture of 26 samples collected from seashores and 49 samples obtained from rivers, including U. prolifera from the Shimanto River, and GenBank data for U. linza and U. procera Ahlner. The samples of the LPP complex differed by only 0–7 substitutions (0–1.149%). Subsequent phylogeographic analyses of the LPP complex based on the 5S rDNA spacer region revealed the presence of two further groupings: a group including 22 strictly marine littoral U. linza samples and a U. prolifera group composed of a mixture of 4 marine samples and all 49 river samples. The monophyly of all river samples indicates that adaptation to low salinity might have occurred only once in the evolutionary history of the LPP complex.     

Ulva (Chlorophyta,Ulvales) Biodiversity in the North Adriatic Sea (Mediterranean,Italy): Cryptic Species and New Introductions

Ulva Linnaeus (Ulvophyceae, Ulvales) is a genus of green algae widespread in different aquatic environments. Members of this genus show a very simple morphology and a certain degree of phenotypic plasticity, heavily influenced by environmental conditions, making difficult the delineation of species by morphological features alone. Most studies dealing with Ulva biodiversity in Mediterranean waters have been based only on morphological characters and a modern taxonomic revision of this genus in the Mediterranean is not available. We report here the results of an investigation on the diversity of Ulva in the North Adriatic Sea based on molecular analyses. Collections from three areas, two of which subject to intense shipping traffic, were examined, as well as historical collections of Ulva stored in the Herbarium Patavinum of the University of Padova, Italy. Molecular analyses based on partial sequences of the rbcL and tufA genes revealed the presence of six different species, often with overlapping morphologies: U. californica Wille, U. flexuosa Wulfen, U. rigida C. Agardh, U. compressa Linnaeus, U. pertusa Kjellman, and one probable new taxon. U. californica is a new record for the Mediterranean and U. pertusa is a new record for the Adriatic. Partial sequences obtained from historical collections show that most of the old specimens are referable to U. rigida. No specimens referable to the two alien species were found among the old herbarium specimens. The results indicate that the number of introduced seaweed species and their impact on Mediterranean communities have been underestimated, due to the difficulties in species identification of morphologically simple taxa as Ulva.     

MOLECULAR ASSESSMENT OF ULVA SPP. (ULVOPHYCEAE,CHLOROPHYTA) IN THE HAWAIIAN ISLANDS1

Sequences of the nuclear internal transcribed spacer 1 (ITS1) region and the chloroplast rbcL gene were obtained from 86 specimens of Ulva (including “Enteromorpha”) from five of the main Hawaiian Islands. These 86 specimens were divided into 11 operational taxonomic units (OTUs) based on analyses of primary sequence data and comparisons of ITS1 secondary structure. Of the 11 OTUs, six have not previously been reported from anywhere in the world. Only three represented exact sequence matches to named species (Ulva lactuca L., syn. U. fasciata Delile; U. ohnoi Hiraoka et Shimada); two others represented exact sequence matches to unnamed species from Japan and New Zealand. Of the 12 species names currently in use for Hawaiian Ulva, only one, U. lactuca (as U. fasciata), was substantiated. General morphology of the specimens did not always correspond with molecular OTUs; for example, reticulate thallus morphology, previously considered diagnostic for the species U. reticulata Forssk., was expressed in thalli assigned to U. ohnoi and to one of the novel OTUs. This finding confirms a number of recent studies and provides further support for a molecular species concept for Ulva. These results suggest that Ulva populations in tropical and subtropical regions consist of species that are largely unique to these areas, for which the application of names based on types from temperate and boreal European and North American waters is inappropriate. Ulva ohnoi, a “green tide” species, is reported from Hawaii for the first time.     

The IMTA-cultivated Chlorophyta Ulva spp. as a sustainable ingredient in Nile tilapia (Oreochromis niloticus) diets

Increasing levels of a mixture of Ulva spp. produced in an integrated multi-trophic aquaculture (IMTA) system were evaluated in Nile tilapia juveniles for partial replacement of dietary fish meal. A control diet (CTRL) was compared with three experimental diets containing 10 % (U10), 15 % (U15), and 20 % (U20) of Ulva spp. meal. Triplicate groups of fish (13 g initial body weight) were fed each diet for 63 days at 26 °C. Nutrient apparent digestibility coefficients and nitrogen retention efficiency did not vary significantly among diets. By the end of the trial, all groups of fish more than tripled their initial body weight. Specific growth rate and final body weight of U10 diet were similar to CTRL and significantly higher than U15 and U20 diets. Increasing Ulva dietary incorporation levels significantly increased feed conversion ratio (FCR), from 1.0 (CTRL) to 1.4 (U20). Fish fed with U10 diet had the highest protein efficiency ratio and nitrogen retention efficiency allowing this fish to growth and reach a final body weight similar to the CTRL group. Protein content was highest in fish fed with the CTRL diet, whereas the highest lipid content was observed in fish fed with U20 diet. The results show that the incorporation of IMTA-produced Ulva meal in Nile tilapia diets is possible up to 10 % without compromising growth performance, protein utilization, and protein retention of juveniles. The high capacity of Nile tilapia to digest all experimental diets suggests that Ulva meal is a practical partial replacement for fish meal in Nile tilapia diets.     

Genetic examination of the type specimen of Ulva australis suggests that it was introduced to Australia

‘Ana‐aosa’, one of the most common marine green algae in Japan, was described as Ulva pertusa Kjellman in 1897 from Hakodate in northern Japan. Ulva pertusa was considered to be a temperate species, with its native distributional range restricted to northeastern Asia. Although this species has been reported from various regions outside northeastern Asia, these records have been explained as non‐indigenous populations. Recently, on the basis of genetic data and nomenclatural priority, U. pertusa was synonymized with U. australis Areschoug, a species described in 1851 from specimens collected in South Australia. Based on genetic studies, Australian populations identified as U. pertusa had been considered to have originated from Japan. However, the published genetic data on U. australis in Australia have been based only on recent collections and no historical specimens have been examined. We tested the hypothesis that native (true) U. australis is an independent species of very similar morphology to U. pertusa, but that its natural domination of shoreline habitats has been suppressed by introduced populations of U. pertusa from Asia. In the present study, we extracted DNA from the type specimen of U. australis housed in the Swedish Museum of Natural History (S) and obtained DNA sequences of the chloroplast rbcL gene and the nuclear rDNA ITS2 region. Our results show that U. australis and U. pertusa are genetically virtually identical, confirming that U. pertusa is a synonym of U. australis. This suggests that the introduction of U. australis to Australia occurred by the middle of the 19th century, when the type was collected and before there was a direct shipping route between Japan and Australia. We speculate that the introduction of U. australis to Australia occurred as a secondary introduction from non‐indigenous populations in northeastern Asia, but not directly from Japan.     

Integrated seaweed cultivation on an abalone farm in South Africa

Land-based abalone aquaculture in South Africa, based on the local species Haliotis midae, started in the early 1990s and has grown rapidly in the last decade, with 13 commercial farms now producing over 850 t per annum. Over 6,000 t per annum of kelp Ecklonia maxima are now harvested for this purpose, and some kelp beds are reaching maximum sustainable limits. Research into seaweed aquaculture as feed (Ulva and some Gracilaria) for abalone started in the late 1990s on the southeast coast (where there are no kelp beds) using abalone waste water. A growing body of evidence suggests that a mixed diet of kelp plus other seaweeds can give growth rates at least as good as compound feed, and can improve abalone quality and reduce parasite loads. A pilot scale Ulva lactuca and abalone integrated recirculation unit using 25% recirculation was designed and built on the south west coast of South Africa using one 12,000-L abalone tank containing 13,200 15 ± 2.5 g abalone, connected to two 3,000-L seaweed tanks containing an initial starting biomass of 10 kg of seaweed, replicated 3 times. In an 18-month period, there were no significant differences in abalone health or growth rates, sediment build up and composition, mobile macro fauna densities and species between the recirculation or the flow-through units. Transfer of oxygen generated by the seaweeds to the abalone tanks was poor, resulting in the recirculated abalone tanks having lower (33%) dissolved oxygen concentrations than a comparable flow-through abalone unit. Seaweed nutrient content and specific growth rates in the units were comparable to seaweeds cultivated in fertilized effluent (SGR = 3.2 ± 3.4%.day⁻¹; Yield = 0.2 ± 0.19 kg.m².day⁻¹). Indications were that at this low recirculation ratio the seaweeds in the units were nutrient limited and that there were no negative effects to the abalone being cultivated in such a recirculation unit at this recirculation ratio.     

Systematics of green algae resembling Ulva conglobata,with a description of Ulva adhaerens sp. nov. (Ulvales,Ulvophyceae)

A phylogenetic and morphological study of green algae resembling Ulva conglobata from Japan was undertaken, along with morphological observations of the original material of U. conglobata Kjellman. The samples resembling U. conglobata included five genetically distinct species: U. fasciata, U. pertusa, U. tanneri, Ulva sp. 1 and Ulva sp. 2. The discovery of marginal denticulations in some of the original material of U. conglobata, made it possible to distinguish those species without denticulations: U. pertusa, U. tanneri and Ulva sp. 2. The morphological characteristics of Ulva sp. 1 matched those of U. conglobata, but Ulva sp. 1 was not clearly identified as U. conglobata owing to the lack of DNA sequence data of the original material. Ulva sp. 2 had lobes adhering to each other by rhizoids. This morphological feature is stable in Ulva sp. 2 and unique among Ulva species. In conjunction with the molecular data, Ulva sp. 2 was described as a new species, U. adhaerens sp. nov. This species features rhizoidal extensions in regions other than the base and an elaborate arrangement of the extensions used for adhesion. It thereby expands our knowledge of the morphogenesis of the morphologically simple genus Ulva.     

Molecular and morphological diversity of Narragansett Bay (RI,USA) Ulva (Ulvales,Chlorophyta) populations

Macroalgal bloom‐forming species occur in coastal systems worldwide. However, due to overlapping morphologies in some taxa, accurate taxonomic assessment and classification of these species can be quite challenging. We investigated the molecular and morphological characteristics of 153 specimens of bloom‐forming Ulva located in and around Narragansett Bay, RI, USA. We analyzed sequences of the nuclear internal transcribed spacer 1 region (ITS1) and the chloroplast‐encoded rbcL; based on the ITS1 data, we grouped the specimens into nine operational taxonomic units (OTUs). Eight of these OTUs have been previously reported to exist, while one is novel. Of the eight OTUs, all shared sequence identity with previously published sequences or differed by less than 1.5% sequence divergence for two molecular markers. Previously, 10 species names were reported for Ulva in Rhode Island (one blade and nine tube‐forming species) based upon morphological classification alone. Of our nine OTUs, three contained blade‐forming specimens (U. lactuca, U. compressa, U. rigida), one OTU had a blade with a tubular stipe, and six contained unbranched and/or branched tubular morphologies (one of these six, U. compressa, had both a blade and a tube morphology). While the three blade‐forming OTUs in Narragansett Bay can frequently be distinguished by careful observations of morphological characteristics, and spatial/temporal distribution, it is much more difficult to distinguish among the tube‐forming specimens based upon morphology or distribution alone. Our data support the molecular species concept for Ulva, and indicate that molecular‐based classifications of Ulva species are critical for proper species identification, and subsequent ecological assessment or mitigation of Ulva blooms.     

INVESTIGATIONS INTO SOUTHERN AUSTRALIAN ULVA (ULVOPHYCEAE,CHLOROPHYTA) TAXONOMY AND MOLECULAR PHYLOGENY INDICATE BOTH COSMOPOLITANISM AND ENDEMIC CRYPTIC SPECIES1

Appreciation of the true species diversity of the genus Ulva in Australian waters has been blinkered by the unproved assumption that its representatives there are largely cosmopolitan. As species of Ulva are some of the longest‐standing and most widely reported taxa of macroalgae, the presumption that they are worldwide in distribution has led to most Australian members being equated with species originally described from extra‐Australian type localities. Ulva species can be notoriously difficult to identify due to the few and often variable characters on which classical taxonomic studies focus so that names of specimens in hand, as well as names appearing in historical distribution records, are frequently difficult or impossible to verify. The combination of morphological and molecular analyses, the latter involving both nuclear (internal transcribed spacer [ITS]) and plastid (rbcL) markers, is critically important in taxonomic studies of the genus and has here been applied to selected Ulva populations from mostly cool‐temperate southern Australian localities. It has been determined that habit‐ and anatomy‐based keys of standard taxonomic literature are largely adequate for assigning species names based on classical concepts, but they often obscure a number of cryptic and pseudocryptic species that do not conform to extra‐Australian populations of the same designation, as indicated by the corresponding molecular data. Here, we present six species (Ulva australis Aresch., U. compressa Forssk., U. fasciata Delile, U. intestinalis L., U. laetevirens Aresch., U. tanneri H. S. Hayden et J. R. Waaland) for which anatomical and molecular data were congruent with both classical concepts and GenBank accession data and confirm these as cosmopolitan taxa in Australia. We also present six putative species designations based on anatomy [U. clathrata (Roth) C. Agardh, U. flexuosa Wulfen, U. linza L., U. prolifera O. F. Müll., U. stenophylla Setch. et N. L. Gardner, U. brisbanensis sp. nov.] that are inconsistent with molecular data, suggesting novel or cryptic taxa not represented in GenBank.     

Protein content, amino acid composition and nitrogen-to-protein conversion factors of Ulva rigida and Ulva capensis from natural populations and Ulva lactuca from an aquaculture system, in South Africa

The South African abalone aquaculture industry is expanding and there is a lack of information on the nutritional profiles of the seaweeds that are used as feed. The current study quantified the protein contents of Ulva rigida and Ulva capensis from natural populations and Ulva lactuca from a commercial, integrated seaweed/abalone aquaculture system. Three methods of protein quantification were used: the Bradford method, crude protein, and specific nitrogen to protein (N-Prot) conversion factors, and results were compared to each other. The results showed that values obtained with the “traditional” conversion factor of 6.25 were on average higher than Bradford values by factors of 64.1 % in U. capensis, 77.1 % in U. rigida and 58.9 % in U. lactuca. This pattern is in line with other published work on seaweed and microalgae. Analyses of amino acid composition showed that aspartic acid was the most abundant amino acid and that these species were also rich in glycine and alanine but poor in histidine, methionine and cysteine. N-Prot factors were as follows: U. capensis, 5.58; U. rigida, 5.12 and U. lactuca, 5.65. An average N-Prot factor of 5.45 provides a more accurate estimate of the protein content of the Ulva species studied than the “traditional” factor of N?×?6.25.     

Does the abundance of girellids and kyphosids correlate with cover of the palatable green algae,Ulva spp.? A test on temperate rocky intertidal reefs

This study assessed whether the abundance of girellids and kyphosids was related to cover of the palatable green algae, Ulva australis and Ulva compressa, on rocky intertidal reefs in Jervis Bay, New South Wales, Australia. No relationship was found between Ulva spp. cover and abundance of Girella tricuspidata, Girella elevata and Kyphosus sydneyanus during a period of relatively low Ulva spp. cover (i.e. February 2011 to March 2011), but during a period of significantly higher Ulva spp. cover (i.e. October 2011 to November 2011) there was a strong correlation between Ulva spp. cover and G. tricuspidata abundance. Spatial analysis indicated that the abundance of G. tricuspidata was consistent across time, suggesting G. tricuspidata were not moving between reefs in response to variation in Ulva spp. cover between periods but rather that large schools of G. tricuspidata resided on reefs that had relatively higher Ulva spp. cover at certain times of the year.     

Growth of <Emphasis Type="Italic">Mytilus galloprovincialis</Emphasis> (mollusca,bivalvia) close to fish farms: a case of integrated multi-trophic aquaculture within the Tyrrhenian Sea

A current practice of marine aquaculture is to integrate fish with low-trophic-level organisms (e.g. molluscs and/or algae) during farming to minimise effects of cultivation on the surrounding environment and to potentially increase economic income. This hypothesis has been tested in the present article experimentally, by co-cultivating fish and mussels (Mytilus galloprovincialis) in the field. Integrated multi-trophic aquaculture (IMTA) experiments were started in July 2004 by transplanting mussel seed at two depths (−3 and −9 m) within 1,000 m downstream to fish cages and at 1,000 m upstream from cages. Mussels were cultured in nylon net bags for 12 months and the growth recorded biometrically. The outcome of our field experiment corroborated the idea of IMTA effectiveness. In fact, in the study area, the organic matter from fish-farm biodeposition caused changes in the chemical environment (i.e. controls and impacted sites were significantly different for organic matter availability and chlorophyll-a) and this induced changes in growth performance of co-cultivated mussels. Mussels cultivated close to cages, under direct organic emission, reached a higher total length, weight and biomass than mussel cultivated far from farms.     

Algal Bioremediation of Waste Waters from Land-Based Aquaculture Using Ulva: Selecting Target Species and Strains

The optimised reduction of dissolved nutrient loads in aquaculture effluents through bioremediation requires selection of appropriate algal species and strains. The objective of the current study was to identify target species and strains from the macroalgal genus Ulva for bioremediation of land-based aquaculture facilities in Eastern Australia. We surveyed land-based aquaculture facilities and natural coastal environments across three geographic locations in Eastern Australia to determine which species of Ulva occur naturally in this region and conducted growth trials at three temperature treatments on a subset of samples from each location to determine whether local strains had superior performance under local environmental conditions. DNA barcoding using the markers ITS and tufA identified six species of Ulva, with U. ohnoi being the most common blade species and U. sp. 3 the most common filamentous species. Both species occurred at multiple land-based aquaculture facilities in Townsville and Brisbane and multiple strains of each species grew well in culture. Specific growth rates of U. ohnoi and U. sp. 3 were high (over 9% and 15% day⁻¹ respectively) across temperature treatments. Within species, strains of U. ohnoi had higher growth in temperatures corresponding to local conditions, suggesting that strains may be locally adapted. However, across all temperature treatments Townsville strains had the highest growth rates (11.2–20.4% day⁻¹) and Sydney strains had the lowest growth rates (2.5–8.3% day⁻¹). We also found significant differences in growth between strains of U. ohnoi collected from the same geographic location, highlighting the potential to isolate and cultivate fast growing strains. In contrast, there was no clearly identifiable competitive strain of filamentous Ulva, with multiple species and strains having variable performance. The fast growth rates and broad geographical distribution of U. ohnoi make this an ideal species to target for bioremediation activities at land-based aquaculture facilities in Eastern Australia.