The fjords are coastal inlets submerged by marine waters present at high latitudes, often covered by glaciers. They represent vulnerable transitional environments characterized by peculiar chemical-physical parameters, which allow the development of a unique fauna. Among the organisms that characterize the complex communities of the fjords, hydroids play a key-role, considering for example important structuring species (habitat formers) with a significant impact on the processes involving the benthos and the water column (benthic pelagic coupling). In this context, the main purpose of the following thesis is the systematic recognition of the hydroid species present in the samples collected in the Chilean Patagonia, in order to characterize their taxonomic and structural diversity. The sampling, which have been collected through SCUBA diving, was performed in 7 stations along the Puyuhuapi fjord (Aysen Region, Chile) in March 2019 at six different depths: 5, 10, 15, 20, 25 and 30 meters. In general, 26 species of hydroids have been identified, of which 19 belonging to the order Leptothecata and 7 to the order Anthoatecata. Most of the species belong to the families of Sertularelliidae (5) and Campanulariidae (3) among the Leptothecata, and to the family of Bougainvillidae (3) among the Anthoathecata. Comparing the species identified by us with those described in previous works conducted in the same fjord, 16 species appear to be new records for the study area considered, while the species Rhysia sp. has never been previously observed in Patagonia. While it was not possible to discern a trend regarding the number of species collected from the "mouth" of the fjord towards the innermost stations, a bathymetric gradient was instead clear, with a smaller number of species collected at the more superficial depths (5 and 10 m), probably in relation to the presence of the superficial brackish water layer. The dataset created on the basis of these samples was then implemented through the collection of data obtained by putting together the information available in the literature, often fragmentary and / or based mainly on local observations, on the hydrozoans present in the fjords worldwide, with the aim of enclose within a single dataset the hydrozoan fauna characterizing the fauna of the fjords. In particular, Norway and Chile represent the geographic areas with the highest number of publications and the highest number of registered species, thus they were considered for further statistical analysis. The analyses carried out show that the two regions, despite having species in common, are significantly different in terms of composition, probably linked to their geographical distance and to the different characteristics (chemical, physical and biological) of the areas considered. Furthermore, as showed from the rarefaction curves of the species diversity of the two regions, the sampling effort applied so far in the Chilean Patagonia seems to be still not sufficient to adequately represent its real biodiversity, with the need for further studies where different types of techniques and targets (e.g. plankton and benthos sampling, acoustic and video investigations, taxonomic and molecular analyses, phylogenetic studies based on DNA barcoding) should be integrated to have a more complete overview, based on an ecosystem approach. In conclusion, this study allowed not only to fill gaps in the knowledge of the species composition and distribution of hydroids in the study area under consideration, but also to summarize the existing knowledge on their worldwide distribution, creating a taxonomic baseline useful in defining possible changes in species composition linked to direct and indirect anthropogenic impacts.
I fiordi sono insenature costiere sommerse dalle acque marine presenti alle alte latitudini, spesso coperti da ghiacciai. Rappresentano vulnerabili ambienti di transizione caratterizzati da parametri chimico-fisici peculiari, che permettono lo sviluppo di una fauna unica nel suo genere. Tra gli organismi caratterizzanti le complesse comunità dei fiordi, gli idroidi ricoprono un ruolo chiave, spesso considerati importanti specie strutturanti con un rilevante impatto sui processi che coinvolgono il benthos e la colonna d’acqua. In questo contesto si inserisce il seguente elaborato di tesi, che ha avuto come scopo principale il riconoscimento sistematico delle specie di idroidi presenti nei campioni raccolti nella Patagonia cilena, al fine di caratterizzarne la diversità tassonomica e strutturale. I campionamenti, avvenuti in immersione subacquea, sono stati condotti in 7 stazioni lungo il fiordo di Puyuhuapi (Regione di Aysen, Chile) a Marzo del 2019 a sei diverse profondità: 5, 10, 15, 20, 25 e 30 metri. In generale, 26 specie di idroidi sono state identificate, di cui 19 appartenenti all’ordine Leptothecata e 7 all’ordine Anthoatecata. La maggior parte delle specie fanno parte delle famiglie di Sertularelliidae (5) e Campanulariidae (3) tra i Leptothecata, e alla famiglia dei Bougainvillidae (3) tra gli Anthoathecata. Confrontando le specie da noi identificate con quelle descritte in lavori precedenti condotti nello stesso fiordo, 16 specie risultano essere nuovi record per l’area di studio considerata, mentre la specie Rhysia sp. non era mai stata precedentemente osservata in Patagonia. Mentre non è stato possibile discernere un trend per quanto riguarda il numero di specie raccolte dalla “bocca” del fiordo verso le stazioni più interne, un gradiente batimetrico è invece risultato chiaro, con un numero minore di specie raccolte alle profondità più superficiali (5 e 10 m), probabilmente in relazione alla presenza dello strato d’acqua salmastro superficiale. Il dataset creato sulla base di questi campioni è stato poi implementato attraverso la raccolta di dati ottenuti mettendo insieme le informazioni disponibili in letteratura, spesso frammentarie e/o basate principalmente su osservazioni locali, sugli idrozoi presenti nei fiordi a livello mondiale, con lo scopo di racchiudere all’interno di un unico dataset la fauna a idrozoi caratterizzante la fauna dei fiordi. In particolare, Norvegia e Cile rappresentano le aree geografiche con il maggior numero di pubblicazioni e il maggior numero di specie registrate, per cui sono state considerate per ulteriori analisi statistiche. Le analisi effettuate mostrano che le due regioni, nonostante presentino specie in comune, hanno una composizione in specie significativamente diversa, probabilmente legata alla loro distanza geografica e alle diverse caratteristiche (chimiche, fisiche e biologiche) delle aree considerate. Inoltre, come risulta dalle curve di rarefazione della diversità delle specie delle due regioni, lo sforzo di campionamento applicato fino ad ora nella Patagonia cilena sembra non essere ancora sufficiente per rappresentare adeguatamente la sua reale biodiversità, con la necessità di ulteriori studi dove diversi tipi di tecniche e target (es. campionamenti di plankton e benthos, indagini acustiche e video, analisi tassonomiche e molecolari, studi filogenetici basati sul DNA barcoding) dovrebbero essere integrati per avere una visione d’insieme più completa, basata su un approccio ecosistemico. In conclusione, questo studio ha permesso non solo di colmare lacune nella conoscenza della composizione in specie e della distribuzione degli idroidi nell’area di studio considerata, ma anche di riassumere le conoscenze esistenti sulla loro distribuzione mondiale, creando una baseline tassonomica utile nel definire possibili cambiamenti nella composizione in specie legati a impatti antropici diretti e indiretti.
IDROZOI CILENI E NON SOLO: LA FAUNA A IDROZOI DEI FIORDI
LATTANZI, PAMELA
2020/2021
Abstract
The fjords are coastal inlets submerged by marine waters present at high latitudes, often covered by glaciers. They represent vulnerable transitional environments characterized by peculiar chemical-physical parameters, which allow the development of a unique fauna. Among the organisms that characterize the complex communities of the fjords, hydroids play a key-role, considering for example important structuring species (habitat formers) with a significant impact on the processes involving the benthos and the water column (benthic pelagic coupling). In this context, the main purpose of the following thesis is the systematic recognition of the hydroid species present in the samples collected in the Chilean Patagonia, in order to characterize their taxonomic and structural diversity. The sampling, which have been collected through SCUBA diving, was performed in 7 stations along the Puyuhuapi fjord (Aysen Region, Chile) in March 2019 at six different depths: 5, 10, 15, 20, 25 and 30 meters. In general, 26 species of hydroids have been identified, of which 19 belonging to the order Leptothecata and 7 to the order Anthoatecata. Most of the species belong to the families of Sertularelliidae (5) and Campanulariidae (3) among the Leptothecata, and to the family of Bougainvillidae (3) among the Anthoathecata. Comparing the species identified by us with those described in previous works conducted in the same fjord, 16 species appear to be new records for the study area considered, while the species Rhysia sp. has never been previously observed in Patagonia. While it was not possible to discern a trend regarding the number of species collected from the "mouth" of the fjord towards the innermost stations, a bathymetric gradient was instead clear, with a smaller number of species collected at the more superficial depths (5 and 10 m), probably in relation to the presence of the superficial brackish water layer. The dataset created on the basis of these samples was then implemented through the collection of data obtained by putting together the information available in the literature, often fragmentary and / or based mainly on local observations, on the hydrozoans present in the fjords worldwide, with the aim of enclose within a single dataset the hydrozoan fauna characterizing the fauna of the fjords. In particular, Norway and Chile represent the geographic areas with the highest number of publications and the highest number of registered species, thus they were considered for further statistical analysis. The analyses carried out show that the two regions, despite having species in common, are significantly different in terms of composition, probably linked to their geographical distance and to the different characteristics (chemical, physical and biological) of the areas considered. Furthermore, as showed from the rarefaction curves of the species diversity of the two regions, the sampling effort applied so far in the Chilean Patagonia seems to be still not sufficient to adequately represent its real biodiversity, with the need for further studies where different types of techniques and targets (e.g. plankton and benthos sampling, acoustic and video investigations, taxonomic and molecular analyses, phylogenetic studies based on DNA barcoding) should be integrated to have a more complete overview, based on an ecosystem approach. In conclusion, this study allowed not only to fill gaps in the knowledge of the species composition and distribution of hydroids in the study area under consideration, but also to summarize the existing knowledge on their worldwide distribution, creating a taxonomic baseline useful in defining possible changes in species composition linked to direct and indirect anthropogenic impacts.| File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12075/8321