Within the family Rhodomelaceae several taxa exhibit significant cryptic diversity and high phenotypic plasticity, requiring the employment of molecular data for the accurate delimitation of genera and species. Among these, the genus Polysiphonia sensu lato has been demonstrated to be polyphyletic, and several new genera have been separated from it over time. This study focuses on Polysiphonia sertularioides, a species with apparently worldwide distribution and a still uncertain taxonomic position. Indeed, previous molecular studies have indicated cryptic diversity within this species and the distinction of several P. sertularioides lineages within the family Rhodomelaceae. Aimed at resolving the taxonomic status of P. sertularioides, morphological and molecular analyses (rbcL and cox1 genes) were carried out on specimens attributable to this taxon and collected from the Mediterranean Sea, including sites near the probable type locality. The obtained results highlight that the Mediterranean P. sertularioides specimens form a phylogenetically well-supported clade, clearly separated from Polysiphonia sensu stricto and from the other Rhodomelacean genera so far described. This result allowed us to propose the establishment of the new genus Neoverlaquea and the new combination Neoverlaquea sertularioides to encompass this group of specimens. Detailed observation of Neoverlaquea morpho-reproductive characters and comparison with the P. sertularioides descriptions published so far allowed us also to find the unique phenotypic traits characterizing this new genus. Moreover, our phylogenetic results confirmed the existence of several phylogenetically distinct extra-Mediterranean lineages morphologically attributed to P. sertularioides, which require further investigation to be correctly identified.

This study investigates the biomass production and growth strategies of the relict seagrass Zostera marina, a species sensitive to high temperatures, within the Venice Lagoon (Italy). Monthly data collected from January to December 2019 and November 2020 to October 2021 in a single station in proximity of one lagoon port-entrance, along with seasonal data from 2018 and 2021 for the whole lagoon, were analyzed in conjunction with environmental parameters and macroalgal presence. The objective was to understand the impact of climate changes, particularly rising water temperatures, on the cover, standing crop and net primary production of Z. marina and the effect of the MoSE gate closures designed to protect Venice from high-water events. Despite expectations of a decline due to temperature increase and reduced water exchange, our findings reveal a notable adaptability of Z. marina, with increases in both cover and biomass. This resilience suggests that Z. marina can counteract environmental challenges, making this study relevant for broader ecological and conservation contexts beyond the Venice Lagoon.

The changes in macrophyte biodiversity and cover from the soft bottoms of 87 stations spread in the entire Venice Lagoon in 2011, 2014, 2018 and 2021 have been analyzed. Results showed a strong macrophyte resilience with an increase in the spread of sensitive macroalgae and aquatic angiosperms, especially Z. noltei and R. cirrhosa, which were not affected by the increase of non-indigenous species (NIS) introduction.The simultaneous analysis of macrophyte variables and the main water and sediment parameters carried out in 2021 highlighted the key role of water transparency and salinity to regulate the vegetation, especially the presence/absence of aquatic angiosperms and sensitive macroalgae. Vice versa, high chlorophyll-a, total suspended solids, nitrogen and silicate concentrations in the water column, and high moisture, low grain-size and phosphorus concentrations in surface sediments favored the presence of opportunistic species, especially Ulva rigida, Gracilariopsis longissima, Agardhiella subulata and Solieria filiformis. The distribution of the aquatic angiosperms and the 41 most widespread macroalgae in association with the main environmental parameters allowed us to highlight their different ecological value, their possible presence/absence and abundance; indeed, their spatial and temporal changes can be excellent tools to determine and predict the ecological status of transitional water systems (TWS).These results carried out in a polyhedric basin such as the Venice Lagoon, composed by a complex of very different microhabitats, can be considered representative of most environmental conditions present in the main TWS of the Italian coastline, and spatial and temporal macrophyte changes can be excellent tools to determine and predict their ecological status evolution.

Dasysiphonia is a genus of the family Delesseriaceae (Rhodophyta) including 9 taxonomically accepted species, among which only the non-indigenous Dasysiphonia japonica has been documented from the Adriatic Sea (Mediterranean). This invasive species is native to Hokkaido Island (Japan) and was introduced to Europe and the Mediterranean Sea through imports of the commercial Pacific oyster Magallana gigas. In this study, we describe a new species belonging to the genus Dasysiphonia, collected in the Mediterranean Sea. This new taxon was sampled in Slovenian coastal waters; its thalli were analysed using both molecular and morphological approaches and it was compared with the other known species. Moreover, samples of the invasive D. japonica were collected from different Venice Lagoon (Italy) sites and used for comparison with the new taxon. The phylogenetic reconstruction, based on the plastid rbcL gene, clearly distinguished the new Slovenian entity from all the known Dasysiphonia species, including the ones recently transferred from the sister genus Dasya. These results indicate that the Slovenian samples represent a new species, hereby named Dasysiphonia adriatica sp. nov.

According to European Union guidelines, the assessment of the ecological status of Transitional Water Systems (TWSs) should be based on the monitoring of biological communities rather than physico-chemical parameters and pollutants. Macrophytes, including aquatic angiosperms and macroalgae, are organisms that respond more quickly to environmental changes by varying the structure and biomass of their assemblages. There are several ecological indices based on macrophytes, among them the Macrophyte Quality Index (MaQI), which has been intercalibrated with water and sediment parameters, nutrient concentrations, and pollutants and is used to determine the ecological status of Italian TWSs. In the Venice Lagoon, it was applied to 87 stations, showing a significant score increase over the last ten years of monitoring (2011–2021) due to progressive lagoon environmental recovery. The dominant taxa assemblages, previously dominated by Ulvaceae, were replaced by species of higher ecological value, with an increase in the number and distribution of sensitive species, as well as the spread and cover of aquatic angiosperms. The rise in the Ecological Quality Ratio (EQR) determined by the MaQI confirms the key role of macrophyte monitoring in detecting environmental changes in TWSs. In fact, a simple check of the presence or absence of aquatic angiosperms and sensitive species is sufficient for an initial rapid assessment of the ecological status of these environments.

Seagrasses play a vital role in marine ecosystems worldwide. However, until recently these ecosystems were experiencing declines due to various global and local threats. In response to this issue, initiatives have been launched to combat seagrass loss by addressing local and regional major stressors and actively engaging in restoration efforts by transplantation. Although seagrass restoration has progressed significantly with the development of numerous transplant techniques, these are not always crowned with success. This is often due to the fact that the environmental parameters of water, sediment and biota of the recipient sites are not carefully considered in their suitability for transplantation. In this study, the multi-year experiences and data from numerous environmental surveys in transitional water systems have been condensed to define limit values for the ideal growth conditions and the extreme values in which the survival of four aquatic angiosperm species is possible: Cymodocea nodosa, Zostera marina, Zostera noltei and Ruppia cirrhosa. Approaches to transplants, seasonality and critical issues have been explored. The identified limits and parameters of water, sediment and biota will help to define the suitability of a recipient site for the rooting of seagrasses, increasing the chances of success for transplant operations.

Salicornia is a highly taxonomically problematic genus due to the reduced morphological observable characters. Ten Eurasian species are currently recognized: S. alpini, S. europaea, S. fruticosa, S. hispanica, S. lagascae, S. perennans, S. perennis, S. persica, S. procumbens, and S. pruinosa. In addition, eleven subspecies are accepted, mainly based on their distribution areas. Along the Venetian coasts and in Sardinia, in the past, an endemic species called S. veneta was recognized, but this name was later synonymized with S. procumbens subsp. procumbens. The aim of the present research is investigating different Italian Salicornia populations by a molecular point of view, using the nuclear ribosomal external transcribed spacer ETS and the plastid psbA-trnH intergenic spacer. A particular focus is on the comparison between Venetian (including those occurring in locus classicus of S. veneta) and Sardinian S. procumbens and other Italian populations of this species. The molecular analyses based on the plastid marker highlight that the Italian S. procumbens populations form two well distinct groups. In particular, some of the Venetian (Locus classicus of S. veneta) and all the Sardinian specimens are genetically distinct (=plastid haplotype 1) from the other investigated populations (=plastid haplotype 2). This indicates that the psbA-trnH haplotype 1 glassworts represent a distinct entity, which we suppose to coincide with the former S. veneta. Therefore, we suggest to recognize this taxonomic entity at the subspecies rank, as S. procumbens subsp. veneta comb. and stat. nov. However, contrary to the results found with the plastid psbA-trnH intergenic spacer, the ETS locus does not show a separation into two distinct clades for S. procumbens, probably due to a different evolution of the two loci. Nevertheless, in the ETS phylogenetic reconstruction, the Sardinian specimens (=ribotypes 2 and 3) are placed, together with a Moroccan sample, in a subclade separated from all the other S. procumbens. These results suggest that the Sardinian populations can represent a subspecies/incipient speciation process, probably due to geographic isolation. In the light of this, morphometric analyses (k-means, MANOVA, PCA, DA, and Box-Plot) have been carried out on the Sardinian and Venetian populations to verify if this distinction is detectable also by a morphological point of view. The morphometric analyses highlight the existence of two groups, concerning both the nuclear and plastid trees. Six characters were found to be diagnostic.

Non-native species are a concern for aquatic environments both for the ecosystem biodiversity and from the economical point of view. The Venice Lagoon is a Mediterranean hotspot of alien introductions and macroalgae are probably the most represented systematic category. For this reason, alien macroalgal distribution and variation were monitored in late spring-autumn surveys, carried out in 2011, 2014, 2018 and 2021 in the soft bottoms of the entire lagoon (87 common stations). Overall, 21 taxa were recorded; three of them (i.e., Acanthosiphonia echinata, Caulacanthus okamurae, Osmundea oederi) are well-established recent introductions for the lagoon, which has increased the total number of non-native species to 33. Ulva australis, previously reported as Ulva laetevirens, is the most abundant species and it is replacing Ulva rigida, especially in the less eutrophic areas. The invasive Gracilariopsis vermiculophylla, an engineering species colonizing the eutrophic choked areas especially in the central lagoon, is instead decreasing. Other abundant established taxa are now dominant components of the lagoon biomass, whereas many others are rare or have small sizes that make their biomass negligible. Overall, these species do not represent serious threats to the environment, but they rather increase biodiversity, with some of them having positive effects on ecosystem services.

Two green microalgal strains, CCCryo 469-16 and CCCryo 470-16, were isolated from samples of Antarctic microflora. Their morphology and 18S rRNA sequences indicated a phylogenetic relationship with strains of the genera Chlorococcum Meneghini, Macrochloris Korshikov, and Pleurastrum Chodat. The last genus is considered particularly problematic as it underwent several revisions. Moreover, its type strain, P. insigne SAG 30.93, was recently demonstrated to coincide genetically with the authentic strain of Chlorococcum oleofaciens from an 18S rRNA phylogeny. This deprived the genus Pleurastrum of an important type reference. Thus, the molecular markers rbcL, tufA, and ITS were employed to identify the Antarctic isolates more precisely. Several other microalgae related to our isolates were obtained from international culture collections for comparison. The obtained results allowed the re-establishment of strain P. insigne SAG 30.93 as the reference strain and the definition of the molecular borders of both genera Pleurastrum and Chlorococcum. Based on our findings, several Chlorococcum species are now re-attributed to Pleurastrum, as well as Macrochloris rubrioleum, here re-named Pleurastrum rubrioleum comb. nov., to which the Antarctic isolates also belong. Finally, a relationship between Pleurastrum lineages and climate zones was established.

We studied the ecological and functional aspects (such as role in sediment characteristics and plant–animal interactions) of a Ruppia cirrhosa (Petagna) Grande meadow during its vegetative season in the choked Valle Campo lagoon, a sub-basin of the wider Valli di Comacchio, on the Northern Adriatic coast. Sampling campaigns were carried out with a roughly fortnightly frequency in 2017 at two sites, one with the Ruppia meadow and one with bare sediment. Sediment parameters analyzed were microphytobenthic chlorophyll-a, protein, carbohydrate, and lipid content, and total organic matter. The macrobenthos was identified at the lowest possible taxonomic level. Chlorophyll a, as a surrogate of microphytobenthos, showed differences between the two sites, probably mainly related to light intensity; thus, it is expected that the absence of seagrass canopy results in the higher production of microphytobenthos. At both sites, proteins were the dominant class of labile compounds, suggesting that detrital organic matter present at both study sites is of high nutritional quality. The high protein/carbohydrate ratio also suggests the presence of non-aged organic matter. We recorded a total of 18 macroinvertebrate taxa. The Ruppia meadow showed a positive influence on macrofauna abundance, diversity, species richness, and composition of trophic groups. Only the infaunal taxa Capitella capitata and Chironomus salinarius exhibited higher abundance at the bare site. The ecological quality status measured by the M-AMBI index was unsatisfactory everywhere. However, the presence of the Ruppia meadow resulted in index values being consistently higher. The role of this minor seagrass has been proved to be of great importance, improving the nutritional quality of the organic matter in the sediments and, above all, providing new habitats and new niches for a number of benthic macrofauna species.

The Mar Piccolo of Taranto (southern Italy, Mediterranean Sea), a site of the European LTER network, is a transitional water system, where a century-old intensive mussel farming activity has been carried out, together with an intense import-export business of bivalve mollusks. Previous studies showed that this basin is third for NIS seaweed introduction in the Mediterranean Sea, after the Thau Lagoon and the Venice Lagoon. The present paper deals with the results of 11-year monitoring activity on non-indigenous species (NIS) of seaweeds, which was performed in the Mar Piccolo. In the studied period (2011–2021), two different time frames (i.e., 2011–2015 and 2016–2021) were considered, since they were based on a different number of sampling sites. To investigate spatial and temporal differences in the seaweed assemblage, a multivariate analysis was performed considering the NIS and the most important native species in terms of temporal occurrence. Fourteen NIS were recorded in total in the Mar Piccolo of Taranto during this period, with variable abundances among sites and years: nine species in the first time period, and thirteen species in the second one. Caulerpa cylindracea , recorded with negligible biomass in the first period, was absent in the second-period samplings. Molecular analyses confirmed the taxonomy of three species (i.e., Grateloupia minima , Neopyropia koreana , and Polysiphonia morrowii ), previously identified only through morphological features. The most abundant species was Hypnea corona , which almost doubled its biomass in the second time period compared to the first one. Three species (i.e., Caulacanthus okamurae , G. minima , and P. morrowii ) increased their biomass by an order of magnitude in the second time period. No significant differences were found over years. Site 1 resulted in significant differences among the sites and different seasonal pattern occurred among the investigated sites. No significant long-term changes occurred in the seaweed assemblages, suggesting the absence of strong disturbances due to the settlement of NIS.

This work studied the potential biotechnological applications of a naviculoid diatom (IMA053) and a green microalga (Tetraselmis marina IMA043) isolated from the North Adriatic Sea. Water, methanol, and dichloromethane (DCM) extracts were prepared from microalgae biomass and evaluated for total phenolic content (TPC) and in vitro antioxidant properties. Biomass was profiled for fatty acid methyl esters (FAME) composition. The DCM extracts had the highest levels of total phenolics, with values of 40.58 and 86.14 mg GAE/g dry weight (DW in IMA053 and IMA043, respectively). The DCM extracts had a higher radical scavenging activity (RSA) than the water and methanol ones, especially those from IMA043, with RSAs of 99.65% toward 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt (ABTS) at 10 mg/mL, and of 103.43% against 2,2-diphenyl-1-picrylhydrazyl (DPPH) at 5 mg/mL. The DCM extract of IMA053 displayed relevant copper chelating properties (67.48% at 10 mg/mL), while the highest iron chelating activity was observed in the water extract of the same species (92.05% at 10 mg/mL). Both strains presented a high proportion of saturated (SFA) and monounsaturated (MUFA) fatty acids. The results suggested that these microalgae could be further explored as sources of natural antioxidants for the pharmaceutical and food industry and as feedstock for biofuel production.

A new species, Blitum venetum Iamonico, Argenti, Sciuto & Wolf is described from the Dolomites Massif (North-Eastern Italy) on the basis of molecular analyses (nuclear ITS and plastid trnL-F regions) and morphological investigation. The new species is similar to B. bonus-henricus and B. californicum, but it differs from these taxa by characters of leaves (width, pubescence, and margins), inflorescence (presence of bracts), perianth segments (colour), and seeds (diameter, colour, and seed testa ornamentation). Moreover, in phylogenetic reconstructions B. venetum results as clearly separated from the other species of the genus; this finding was further strengthened by the nucleotide divergences calculated between the sequence of the type specimen and other Blitum taxa, which are comparable with the interspecific divergences calculated inside this genus.

In the last decade, the Venice Lagoon showed a significant environmental recovery that changed the assemblages of macroalgal and aquatic angiosperm dominant species and significantly increased the primary production. The decreasing of anthropogenic impacts, such as eutrophication and clam harvesting, favored a strong reduction of Ulvaceae, replaced by species with higher ecological value, and the recolonization of aquatic angiosperms. Consequently, hypo-anoxic conditions, once frequently occurring in the lagoon, have been considerably reduced and aquatic angiosperms have recolonized the area, covering 94.8 km(2) in comparison to the 55.9 km(2) recorded in 2003 (+70%). Cymodocea nodosa, Zostera marina, and Zostera noltei expanded by 37.5%, 44.6%, and 191%, respectively, with a significant increase in biomass and primary production. In late spring 2018, angiosperms showed a standing crop of approximately 372 ktonnes (+77%) and a net primary production of approximately 1189 ktonnes FW (+67%). In the meantime, Ruppia cirrhosa, which since the 1980s had disappeared from the lagoon areas subjected to tidal expansion, but was still present in some fishing valleys, recolonized the bottoms of the northern lagoon with meadows of over 6 km(2); this accounted for a standing crop and net primary production of 8.9 and 18.0 ktonnes, respectively. Based on surveys carried out in 2021, ecological conditions are still improving, and this is increasing both the biodiversity and the production of macroalgae and aquatic angiosperms.

Over the last decade, our knowledge of the phylogenetic and taxonomic diversity of coralline algae has greatly progressed thanks to the use of DNA sequence data. Despite this, in some geographic regions the knowledge of coralline diversity is still incomplete, because it is entirely based on traditional morpho-anatomical grounds; Antarctica can certainly be included among these regions. During an investigation of the marine phototrophic biodiversity of the Ross Sea, a crustose coralline alga was collected from two sites in Tethys Bay. The alga formed thin crusts adherent to cobbles at ~20 m depth and showed morpho-anatomical features typical of the order Hapalidiales, family Hapalidiaceae (cell fusions, zonate tetrasporangia produced in multiporate conceptacles, and apical plugs). Molecular phylogenies based on the psbA, rbcL and 18S rRNA genes showed that this alga formed a lineage in the family Hapalidiaceae for which a formal assignment at genus level was not yet available. The only other known member of the lineage was a coralline from the Balleny Islands, named as Hapalidiaceae sp. ASG448A, for which psbA and 18S rRNA sequences were deposited in GenBank without identification at genus and species level. Based on our results, we describe this lineage as the new genus Tethysphytum Sciuto, Moschin & Moro, with the single species Tethysphytum antarcticum Sciuto, Moschin & Moro. At present, morpho-anatomical characters do not allow for the discrimination of Tethysphytum from other similar genera of Hapalidiaceae. The discovery of a new genus suggests that the diversity of coralline algae in Antarctica may have been underestimated and that molecular data will be essential for future taxonomic assessments of this group within this region.

During samplings aimed at isolating microalgal strains, a coccoid greyish-green alga was collected along the North Adriatic coasts (Mediterranean Sea, Italy) and grown in culture. The microalgal strain (named strain B1A) was then subjected to an integrative taxonomy approach in order to correctly identify it. Morphological and ultrastructural observations and phycobiliprotein content analysis were carried out, as well as molecular analyses based on the 18S rRNA, rbcL, psbA and plastid-encoded 23S rRNA genes. Phylogenetic placement and ultrastructural observations clearly indicated that strain B1A is a member of the red microalgal genus Dixoniella (Rhodellophyceae, Proteorhodophytina) and is distinct from the only species so far described for this taxon. Therefore, a new species was described to encompass the isolate from the North Adriatic Sea and another isolate from Japan (MF-G2), which was phylogenetically related to strain B1A: Dixoniella giordanoi sp. nov.

One of the main requirements of any sound biological monitoring is the availability of long term and, possibly, temporal data with a high resolution. This is often difficult to be achieved, especially in Antarctica, due to a variety of logistic constraints, which make continuous sampling and monitoring activities generally unfeasible. Here we focus on the 5 μm filters used in the desalination plant of the Italian research base "Mario Zucchelli" in the Terra Nova Bay area (Ross Sea, Antarctica) to evaluate intra-annual coastal nanoplankton dynamics. These filters, together with others of larger mesh sizes, are used to decrease the amount of organisms and debris in the input seawater before the desalination processes take place, hence automatically collect the plankton present in the water column around the desalination system intake. We have used a DNA metabarcoding approach to characterize the communities retained by filters' sets collected in January 2012 and 2013. Intra-annual dynamics were disclosed with an unprecedented detail, that would not have been possible by using standard sampling approaches, and highlighted the importance of extreme, stochastic events such as katabatic wind pulses, which triggered dramatic, short-term shifts in coastal nanoplankton composition. This method, by combining a cost-effective sampling and molecular techniques, may represent a viable solution for long-term monitoring programs focusing on Antarctic coastal communities.

Radicilingua Papenfuss and Calonitophyllum Aregood are two small genera of the family Delesseriaceae that consist of only three and one taxonomically accepted species, respectively. The type species of these genera, Radicilingua thysanorhizans from England and Calonitophyllum medium from the Americas, are morphologically very similar, with the only recognized differences being vein size and procarp development. To date, only other two species were recognized inside the genus Radicilingua: R. adriatica and R. reptans. In this study, we analysed specimens of Radicilingua collected in the Adriatic and Ionian Sea (Mediterranean), including a syntype locality of R. adriatica (Trieste, northern Adriatic Sea), alongside material from near the type locality of R. thysanorhizans (Torpoint, Cornwall, UK). The sequences of the rbcL-5P gene fragment here produced represent the first molecular data available for the genus Radicilingua. Phylogenetic reconstruction showed that the specimens from the Adriatic and Ionian Seas were genetically distinct from the Atlantic R. thysanorhizans, even if morphologically overlapping with this species. A detailed morphological description of the Mediterranean specimens, together with an accurate literature search, suggested that they were distinct also from R. adriatica and R. reptans. For these reasons, a new species was here described to encompass the Mediterranean specimens investigated in this study: R. mediterranea Wolf, Sciuto & Sfriso. Moreover, in the rbcL-5P tree, sequences of the genera Radicilingua and Calonitophyllum grouped in a well-supported clade, distinct from the other genera of the subfamily Nitophylloideae, leading us to propose that Calonitophyllum medium should be transferred to Radicilingua.

Ulva australis Areschoug (Ulvales, Chlorophyta) is traditionally used as a foodstuff in Korea and to treat several diseases, such as hyperlipidemia and urinary ailments. It is now considered an invasive species of the Venice Lagoon (Italy). This work explored U. australis as a potential source of bioactive molecules with biotechnological applications. For that purpose, organic and water extracts were prepared from dried biomass of U. australis and evaluated for radical scavenging activity (RSA), metal chelating activities and for in vitro inhibition of enzymes related with several disorders, namely Alzheimer's disease (acetylcholinesterase, butyrylcholinesterase), hyperpigmentation (tyrosinase), obesity (lipase), Type-2 diabetes mellitus (alpha-glucosidase, alpha-amylase) and skin sagging (elastase). Extracts were also evaluated for total contents of phenolics, flavonoids condensed tannins and carbohydrates. Finally, the fatty acids methyl esters profile of the biomass was established by gas chromatography-mass spectrometry. Extracts had low to moderate radical scavenging activity on DPPH, and a higher ability to chelate Fe2+ than Cu2+, and the maximum Fe2+ chelating capacity was observed in the tincture (IC50 = 4.82 mg/mL). Samples had a higher ability to inhibit alpha-amylase and microbial alpha-glucosidase than the other tested enzymes. The biomass of U. australis presented a highly saturated fatty acids profile, enriched in palmitic acid. These data suggest U. australis as a promising source of natural products with anti- diabetic properties and as a desirable species for biodiesel production.

Microcalcareous epiphytic seaweeds (MES) are macroalgae more sensitive than aquatic angiosperms to environmental degradation and, with their presence/absence, these species act like sentinels providing useful information on the ecological status of environments. In this study, we analyzed the environmental parameters in water column and surface sediments in relation to macrophyte variables from 257 sites, distributed in the main Italian transitional water systems (TWS). The results showed that MES are strongly correlated to pH changes, the main parameter that regulates their presence/absence. The optimal growth range is between pH 7.80 and 8.35; out of these values their growth is reduced or hampered. In oxidized sediments the carbonate crusts, composed by Mg-Calcite (an unstable compound that in the sediments quickly turns into calcite), can permanently trap up to 2.47 tonnes ha(-1) yr(-1) of CO2, increasing sediment thickness of approx. 0.06-0.21 mm yr(-1).