Native Macroalgal Species Research Articles

Growth rates of Gracilariopsis longissima, Gracilaria bursa-pastoris and Chondracanthus teedei (Rhodophyta) cultured in ropes: implication for N biomitigation in Cadiz Bay (Southern Spain)

Cultures of three native macroalgal species (Gracilariopsis longissima, Gracilaria bursa-pastoris and Chondracanthus teedei) were developed in open coastal waters of a shallow, potentially eutrophic bay in Southern Spain. Experimental trials to assess the technical feasibility of seaweed cultivation and nitrogen biofiltration potential were conducted between October 2014 and December 2015. Seaweeds were cultivated using submersible rafts in five periods of 9 weeks to identify the most suitable seasons and culture duration (3, 6 or 9 weeks). Using generalized linear models (GLMs), the most relevant environmental factors controlling the growth of the three seaweeds were identified. Maximum net growth rates varied between 1.39% day−1 in C. teedei (winter, 6 weeks) and 4.71% day−1 in G. longissima (autumn, 3 weeks). Overall, the best period to cultivate seaweeds in Cadiz Bay was from mid-winter to early summer. No clear effects of duration of the culture were observed for C. teedei and G. bursa-pastoris. Short culture periods of 3 weeks were more suitable for G. longissima. Tissue N contents generally were lower than the critical quota, and GLMs suggested a critical role of N limiting seaweed growth in this bay. Dissolved inorganic nitrogen was biofiltered from winter to early summer and revealed G. bursa-pastoris as the main biomitigator of nitrogen (up to 80 mg N m−1 month−1 in spring). This species also showed positive growth rates virtually during the entire study period and was the most suitable species for cultivation in this area.

Nutrient (N and P) dynamics of the invasive macroalga Gracilaria vermiculophylla: nutrient uptake kinetics and nutrient release through decomposition

The invasive alga Gracilaria vermiculophylla was introduced to Europe two decades ago and has since become dominant in many shallow estuaries. Gracilaria vermiculophylla is a relatively fast-growing alga that thrives well at low nutrient availability in summer, suggesting that it uses nutrients efficiently, which might give it a competitive advantage over many native species. We studied therefore the nutrient dynamics of G. vermiculophylla and compared it to those of a range of native macroalgal species. Nutrient uptake rates ( $${\text{NH}}_{4}^{ + }$$ , $${\text{NO}}_{3}^{ - }$$ and $${\text{PO}}_{4}^{3 - }$$ ) were compared to growth-related requirements and we found that G. vermiculophylla needs relatively high nutrient concentrations to sustain fast and non-limited growth. This compares to the nutrient dynamics of many fast-growing algae, and we found thus no indication that G. vermiculophylla should have any particular advantage relative to other, sympatric species. The nutrient storage capacity of G. vermiculophylla was, in contrast, relatively large and comparable to that of more slow-growing algae, which, when combined with the low nutrient uptake experienced in summer, could explain how G. vermiculophylla can sustain non-nutrient limited growth through most of the growth season. The biomass of G. vermiculophylla can be massive and estimates showed that gross nutrient uptake could exceed the amount of nutrients received from land. The turnover of Gracilaria biomass is, however, fast and nutrients bound in the resulting detritus are quickly mineralized during decomposition, which is especially important during late summer when water temperatures are high. Invasion and subsequent dominance by G. vermiculophylla may thus affect local nutrient cycling significantly.

Importance of the invasive macroalga Undaria pinnatifida as trophic subsidy for a beach consumer

Food webs on sandy beaches rely heavily on spatial subsidies of macroalgae and other detritus. Invasive macroalgal species are modifying many ecosystems worldwide, so the potential exists for them to alter the quantity and quality of food available to sandy beach consumers. We evaluated the suitability of the invasive kelp Undaria pinnatifida as a food for the talitrid amphipod Bellorchestia quoyana, an abundant consumer on sandy beaches in southern New Zealand. U. pinnatifida had similar gross nutritional and biomechanical properties to the three native macroalgal species (the kelps Macrocystis pyrifera and Durvillaea antarctica, and the green Ulva spp.). B. quoyana consumed U. pinnatifida at similar or higher rates than the native kelps in laboratory feeding assays (choice and no-choice assays with fresh tissues, and choice assays with tissue reconstituted into agar foods to remove structural properties). Our results indicate that U. pinnatifida is a usable alternative food source for B. quoyana and could, therefore, contribute to the local sandy beach food web. Understanding the role that invasive macroalgae play as a food source for beach consumers is essential to better comprehend how they may affect these subsidy-dependent ecosystems.

Nonnative Seashore Paspalum,Paspalum vaginatum(Poaceae), Consumed by Hawaiian Green Sea Turtles (Chelonia mydas): Evidence for Nutritional Benefits

The Hawaiian green turtle, Chelonia mydas Linnaeus, is a marine herbivore known to feed on sea grasses and seaweeds. On the east side of the island of Hawai‘i, at high tide, green turtles have been observed feeding on a terrestrial, salt-tolerant turfgrass: seashore paspalum, Paspalum vaginatum Swartz, first introduced to the Hawaiian Islands in the 1930s. The role of this grass in green turtle nutrition is unknown. Paspalum vaginatum samples were collected at Keaukaha Beach Park, Hilo, and analyzed for nutritional composition (percentage water, percentage ash, caloric value, C : N ratio, percentage protein, and percentage lignin). In addition, two red seaweeds, Pterocladiella capillacea (Gmelin) Santelices & Hommersand, a common food source for green turtles, and Ahnfeltiopsis concinna (J. Agardh) Silva & DeCew, an abundant high-intertidal species sometimes consumed by turtles, were analyzed for comparison. In contrast to the two seaweed species, Paspalum vaginatum contained approximately half the ash; 300–1,500 more calories/g ash-free dry weight; three to four times greater total protein; and 3–19 times higher lignin content. Green turtles in Hawai‘i may opportunistically consume P. vaginatum because of its local abundance and/or its high protein and caloric content. In foraging areas where native macroalgal species have declined and/or turtle carrying capacity has been reached, green turtles may exploit new foods, such as seashore paspalum, and perhaps mitigate decline in somatic growth rates and body condition.

Invader traits and community context contribute to the recent invasion success of the macroalga Heterosiphonia japonica on New England rocky reefs

The successful establishment and spread of invasive species may be determined by intrinsic traits of the invader, characteristics of the invaded community, and interactions between the two. The red filamentous macroalga Heterosiphonia japonica has recently invaded and expanded its range in the northwestern Atlantic. We surveyed and compared macroalgal communities at sites with different levels of invasion in Nahant, Massachusetts, and examined potential factors contributing to Heterosiphonia’s successful invasion by assessing its growth rates and rates of herbivory by native grazers in the laboratory. We evaluated growth and herbivory for isolated individuals and for individuals within a macroalgal assemblage comprised of the most abundant species in the native community. We also measured macroalgal nitrate uptake rates to examine a potential mechanism underlying observed differences in growth rate. High abundances of Heterosiphonia were associated with lower native macroalgal species richness, evenness, and diversity and with differences in species composition in the field. Experiments showed that rates of growth and grazing were context dependent. In isolation, Heterosiphonia grew comparably and was grazed similarly to the two native filamentous macroalgae. Within the context of the native macroalgal assemblage, it grew much faster than all common native species, experienced reduced herbivory from one native grazer, and increased herbivory from another. Consistent with its faster growth, Heterosiphonia was the most efficient at nitrate uptake. Our results suggest that multiple interactions between intrinsic traits (e.g., competitiveness for nutrients) and extrinsic factors (e.g., presence of native macroalgal species, identity and relative abundances of native grazers) contribute to Heterosiphonia’s invasion success.

Faunal differences between the invasive brown macroalga Sargassum muticum and competing native macroalgae

Interactions between macroalgae and their associated fauna are of great interest for marine invasions, because fauna may increase the biotic resistance of a system and macroalgal invasions may cause shifts in faunal composition. We tested for differences in faunal community structure between a macroalgal invader, Sargassummuticum, and several native macroalgae in intertidal pools on both the west and south coast of Portugal. On each coast, we compared the faunal diversity and composition associated with the invader with that of the competing native macroalga(e). On the west coast, the diversity of the fauna associated with S. muticum was equal to or lower than with the native competitor, Cystoseira humilis. Fauna composition differed between S. muticum and C. humilis at both locations, but within each species, no differences between locations were detected. In contrast, the fauna diversity on S. muticum of the south coast varied among locations. S. muticum fauna differed from the fauna of all native macroalgae at one location, but only from three out of seven native macroalgae at the other location. Discriminating fauna species did not show a consistent pattern towards higher or lower abundances in S. muticum compared to most native macroalgae, and species-specific contributions were small. Differences in fauna community also depended on the identity of the native macroalga. In conclusion, the fauna associated with S. muticum differs from many native brown macroalgae, but these differences were not consistent as they depend both on the native macroalgal species and on location. This invader does not seem to have a severe negative impact on local macroalgae-associated fauna.

Effects of habitat-modifying invasive macroalgae on epiphytic algal communities

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 400:87-100 (2010) - DOI: https://doi.org/10.3354/meps08391 Effects of habitat-modifying invasive macroalgae on epiphytic algal communities Emily Jones1,2,*, Carol S. Thornber1 1Department of Biological Sciences, University of Rhode Island, Kingston, Rhode Island 02881, USA 2Bodega Marine Laboratory, University of California Davis, Bodega Bay, California 94923, USA *Email: emjones@ucdavis.edu ABSTRACT: Although invasive species can negatively impact communities via processes such as resource competition, they may also add new resources that facilitate the distribution and/or abundance of other organisms. In rocky intertidal systems, many benthic macroalgae compete for primary substrate, while providing secondary substrata to which sessile organisms can attach. Using field surveys and laboratory experiments, we investigated algal host–epiphyte dynamics in a New England rocky intertidal system. First, we compared the composition, abundance, richness, and diversity of epiphytes on 2 invasive macroalgal species, Codium fragile ssp. tomentosoides and Grateloupia turuturu, to 2 native macroalgal species, Chondrus crispus and Fucus vesiculosus. We found significant differences among epiphyte communities, as all macroalgal hosts supported different assemblages of species. While epiphyte richness and diversity were generally low on F. vesiculosus and G. turuturu year-round, they were low on C. crispus during the winter only. In contrast, epiphyte richness and diversity on C. fragile remained high throughout the year, suggesting that C. fragile plays an important role for supporting epiphytes during the cooler months. Second, we examined the relationship between epiphytes and a common herbivorous snail, Lacuna vincta. The abundance of juvenile L. vincta was positively correlated with 1 of the 2 most common epiphyte species, Neosiphonia harveyi. However, L. vincta showed a significant consumption preference for the other abundant epiphyte, Ceramium virgatum, in laboratory assays. Our results suggest that epiphyte facilitation by these invasive algal hosts is not only seasonally important for maintaining species richness and diversity, but may also provide both food and habitat for higher trophic levels. KEY WORDS: Invasive macroalgae · Epiphyte · Habitat-modification · Codium fragile · Grateloupia turuturu · Lacuna vincta Full text in pdf format PreviousNextCite this article as: Jones E, Thornber CS (2010) Effects of habitat-modifying invasive macroalgae on epiphytic algal communities. Mar Ecol Prog Ser 400:87-100. https://doi.org/10.3354/meps08391 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 400. Online publication date: February 11, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.

Facilitative effects of introduced Pacific oysters on native macroalgae are limited by a secondary invader, the seaweed Sargassum muticum

Introduced habitat-providing organisms such as epibenthic bivalves may facilitate the invasion and expansion of further non-native species which may modify the effects of the primary invader on the native system. In the sedimentary intertidal Wadden Sea (south-eastern North Sea) introduced Pacific oysters ( Crassostrea gigas) have overgrown native blue mussel beds ( Mytilus edulis). These oyster beds are now providing the major attachment substratum for macroalgae. Recently, oysters have expanded their distribution into the shallow subtidal zone of the Wadden Sea, and there support a rich associated species community including the Japanese seaweed Sargassum muticum, which has been presumably introduced together with the oysters. With a block designed field experiment, we explored the effects of S. muticum on the associated community of soft-bottom C. gigas beds in the shallow subtidal. Replicated oyster plots of 1 m 2 were arranged with a density of 0, 7, 15 or 45 S. muticum m − 2 , respectively. We found no effects of different S. muticum densities on associated epi- and endobenthic community compositions associated to the oyster plots. However, the overall coverage of sessile organisms settling on the oyster shells was significantly reduced at high S. muticum densities. The occurrence of abundant native macro-algal species such as Polysiphonia nigrescens, Antithamnion plumula and Elachista fucicola decreased with increasing S. muticum densities. Sessile invertebrates, by contrast, were only marginally affected and we found no effects of S. muticum canopy on diversity and abundance of endofauna organisms. We conclude that increasing densities of S. muticum on C. gigas beds in the shallow subtidal zone of the Wadden Sea limit the occurrence of native macroalgae which otherwise would benefit from the additional hard substratum provided by the oysters. Thus, a secondary invader may abolish the effects of the primary invader for native species by occupying the new formed niche.

The extent of grazing release from epiphytism forSargassum muticum(Phaeophyceae) within the invaded range

The overall biotic pressure on a newly introduced species may be less than that experienced within its native range, facilitating invasion. The brown algaSargassum muticum(Yendo) Fensholt is a conspicuous and successful invasive species originally from Japan and China. We comparedS. muticumand native macroalgae with respect to the biotic pressures of mesoherbivore grazing and ectocarpoid fouling. In Strangford Lough, Northern Ireland,S. muticumthalli were as heavily overgrown with seasonal blooms of epiphytic algae as native macroalgal species were. The herbivorous amphipodDexamine spinosawas much more abundant onS. muticumthan on any native macroalga. When cultured with this amphipod,S. muticumlost more tissue than three native macroalgae,Saccharina latissima(Linnaeus) Laneet al.,Halidrys siliquosa(Linnaeus) Lyngbye andFucus serratusLinnaeus.Sargassum muticumcultured with both ectocarpoid fouling and amphipods showed a severe impact, consistent with our previous findings of large declines in the density ofS. muticumobserved in the field during the peak of fouling. Despite being a recent introduction into the macroalgal community in Strangford Lough,S. muticumappears to be under biotic pressure at least equal to that on native species, suggesting that release from grazing and epiphytism does not contribute to the invasiveness of this species in Strangford Lough.

Release from native herbivores facilitates the persistence of invasive marine algae: a biogeographical comparison of the relative contribution of nutrients and herbivory to invasion success

The effect of herbivory and nutrient enrichment on the growth of invasive and native macroalgal species was simultaneously studied in two biogeographic regions: the Caribbean and Hawaii. Herbivores suppressed growth of invasive algae in their native (Caribbean) and invaded range (Hawaii), but despite similar levels of herbivore biomass, the intensity of herbivory was lower in Hawaii. Algal species with a circumtropical distribution did not show a similar effect of herbivores on their growth. Nutrient enrichment did not enhance growth of any algal species in either region. The reduction in herbivore intensity experienced by invasive algae in Hawaii rather than an escape from (native) herbivores provided invasive macroalgae with “enemy release” sensu the Enemy Release Hypothesis (ERH). Since native, Hawaiian herbivores still feed and even prefer invasive algae over native species, invasion scenario’s that involve predation (e.g. the ERH) could be falsely dismissed when invasive species are only studied in their invasive range. We therefore argue that escape from herbivores (i.e. enemy release) can only effectively be determined with additional information on the intensity of predation experienced by an invasive species in its native range.

Threat to macroalgal diversity: effects of the introduced green alga Caulerpa racemosa in the Mediterranean

Caulerpa racemosa is a tropical green alga introduced into the Mediterranean probably as an immigrant from the Red Sea. This study evaluated the modifications caused by C. racemosa invasion on the structure of the benthic macroalgal community near Leghorn (northwestern Mediter- ranean). To achieve this objective, we studied invasion by C. racemosa of algal assemblages on 2 dif- ferent substrata by monitoring the structure of the phytobenthic community before and after the inva- sion of the alga and comparing our results with assemblages not invaded by C. racemosa. Results showed that the invasive alga Caulerpa racemosa completely covered the surface of both types of substratum 6 mo after the start of the invasion. With rapid horizontal elongation of the stolons (up to 2 cm d -1 ) C. racemosa overgrew native macroalgal species within 4 mo. As a consequence, phyto- benthic community structure deeply changed: species cover, number and diversity greatly decreased. Furthermore, the relative importance among vegetation layers of the macroalgal assem- blage changed: turf and encrusting species were deeply affected while erect species survived after 1 yr of the invasion. During the period from December to May, when both cover and biomass of C. racemosa diminished, the macroalgal community did not return to initial conditions. Instead, the structural changes increased in the following season, indicating the importance of C. racemosa inva- sion on a local scale.

Macroalgae, in the Upper Yarra and Watts River catchments: Distribution and Phenology

Studies on the floristics and phenology of macroalgal communities in the upper Yarra and Watts River catchments have shown that the urbanized reaches of the Yarra River near Warburton are relatively species-rich and that they include nearly all macroalgal taxa found in protected catchments upstream. The lower of three river sites near Warburton, however, includes fewer species and is seasonally dominated by Vaucheria bursata, a saproxenous alga. The macroalgal communities on solid rock are distinct from those on loose rock subject to flood movement, and they include more taxa with basally attached filaments. A nearby enriched tributary, McMahons Creek, is dominated by a Spirogyroideae species and is species-poor. Species richness is also low on small-weirs and natural stream habitats in protected upstream catchments. Experimental timber harvesting above a series of small-weirs introduced weed species into the streams, replacing some of the native macroalgal species. Indigenous macroalgal species return 5 or so years after selective timber thinning, but they do not return even 10 years after clear-felling and fertilizing. The macroalgae of the upper Yarra River basin can be grouped into those that can grow throughout the year, those whose growth is restricted by water temperature, and those with a distinct seasonality unrelated to water temperature.