Macroalgae are a vital component of transitional water sytems, where they provide several ecosystem services. Indeed, they maximally contribute to photosynthetic oxygen production, as well as providing food and shelter for adults and juveniles of vertebrate and invertebrates. Moreover, they are important indicators for the evaluation of these environment ecological status (Sfriso et al 2014). For this reason, the continuous monitoring of the health state of their communities is paramaount. The Mar Piccolo of Taranto is one of the most studied transitional water systems in the Mediterranean, and a site of the eLTER Infrastructure, due to the availability of historical data on the phytobenthic communities, dating back to the Twenties of the last century. In the last years, this environment has aroused a noticeable scientific interest, since it ranked third in the Mediterranean Sea for the number of alien species, introduced mainly through the import-export of bivalve molluscs. However, it should be stressed that the Mar Piccolo houses also very rich populations of native species, which seem to coexist peacefully with alien species, as showed by recent studies (Denti et al. 2024). The seasonal observations, sistematically carried out since 2011 until 2023 in six stations (three in the First Inlet and three in the Second Inlet), showed that one of these natives, i.e., Chondracanthus acicularis (Roth) Fredericq. This red algae underwent a noticeable abundance development over these years; its total biomass reached a peak of 11.6 kg fw m-2 in 2017, being the second most abundant macroalgal species, only surpassed by another native species, i.e., Dictyota dichotoma (Hudson) J.V. Lamouroux var. intricata (C. Agardh) Greville (Ochrophyta, Dictyotales), which reached a total biomass of 12.1 kg fw m-2. Except for 2011 and 2020-2022, when other either native or alien species overtook it, in the other years, C. acicularis was either the fourth or the fifth most abundant species on a mean number of 68 macroalgal species. It was observed always in the attached habitus, almost exclusively in the Second Inlet, with peaks of abundance in the only two stations where natural hard substrata are present. Attached thalli were present throughout the year, anyway no marked seasonal preference was observed for C. acicularis, since the biomass peak was reached in different seasons, in the different years. In the Mar Piccolo, this species was not observed in the Twenties (Pierpaoli 1923). The first record was in 1987 (as Gigartina acicularis (Roth) J.V. Lamouroux), and then again in 2009, but with biomass value considerably lower. Chondracanthus acicularis is included in the list of “sensitive species”, indicating a good environmental status (Sfriso et al. 2014). It’s progressive development in the Mar Piccolo can be considered another evidence of the basin recovery, which has been taking place for several years (Petrocelli et al. 2019), as already reflected by the luxuriant meadow of Cymodocea nodosa (Ucria) Ascherson, as well as the resumption of sexual reproduction by many species, which reproduced only vegetatively for a long time. Moreover, considering that recent analysis showed the presence of bioactive compounds of lipidic nature (Denti pers. comm.), it is surely reasonable to expect that it will become also a precious nutrient resource for the local fauna.

Chondracanthus acicularis (Rhodophyta, Gigartinales) in the Mar Piccolo of Taranto.

Denti Giuseppe;Cecere Ester;Portacci Giuseppe;Petrocelli Antonella
2024

Abstract

Macroalgae are a vital component of transitional water sytems, where they provide several ecosystem services. Indeed, they maximally contribute to photosynthetic oxygen production, as well as providing food and shelter for adults and juveniles of vertebrate and invertebrates. Moreover, they are important indicators for the evaluation of these environment ecological status (Sfriso et al 2014). For this reason, the continuous monitoring of the health state of their communities is paramaount. The Mar Piccolo of Taranto is one of the most studied transitional water systems in the Mediterranean, and a site of the eLTER Infrastructure, due to the availability of historical data on the phytobenthic communities, dating back to the Twenties of the last century. In the last years, this environment has aroused a noticeable scientific interest, since it ranked third in the Mediterranean Sea for the number of alien species, introduced mainly through the import-export of bivalve molluscs. However, it should be stressed that the Mar Piccolo houses also very rich populations of native species, which seem to coexist peacefully with alien species, as showed by recent studies (Denti et al. 2024). The seasonal observations, sistematically carried out since 2011 until 2023 in six stations (three in the First Inlet and three in the Second Inlet), showed that one of these natives, i.e., Chondracanthus acicularis (Roth) Fredericq. This red algae underwent a noticeable abundance development over these years; its total biomass reached a peak of 11.6 kg fw m-2 in 2017, being the second most abundant macroalgal species, only surpassed by another native species, i.e., Dictyota dichotoma (Hudson) J.V. Lamouroux var. intricata (C. Agardh) Greville (Ochrophyta, Dictyotales), which reached a total biomass of 12.1 kg fw m-2. Except for 2011 and 2020-2022, when other either native or alien species overtook it, in the other years, C. acicularis was either the fourth or the fifth most abundant species on a mean number of 68 macroalgal species. It was observed always in the attached habitus, almost exclusively in the Second Inlet, with peaks of abundance in the only two stations where natural hard substrata are present. Attached thalli were present throughout the year, anyway no marked seasonal preference was observed for C. acicularis, since the biomass peak was reached in different seasons, in the different years. In the Mar Piccolo, this species was not observed in the Twenties (Pierpaoli 1923). The first record was in 1987 (as Gigartina acicularis (Roth) J.V. Lamouroux), and then again in 2009, but with biomass value considerably lower. Chondracanthus acicularis is included in the list of “sensitive species”, indicating a good environmental status (Sfriso et al. 2014). It’s progressive development in the Mar Piccolo can be considered another evidence of the basin recovery, which has been taking place for several years (Petrocelli et al. 2019), as already reflected by the luxuriant meadow of Cymodocea nodosa (Ucria) Ascherson, as well as the resumption of sexual reproduction by many species, which reproduced only vegetatively for a long time. Moreover, considering that recent analysis showed the presence of bioactive compounds of lipidic nature (Denti pers. comm.), it is surely reasonable to expect that it will become also a precious nutrient resource for the local fauna.
2024
Istituto di Ricerca sulle Acque - IRSA - Sede Secondaria Taranto
transitional waters, Mar Piccolo, macroalgae, sensitive species
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.14243/516408
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