Hypoxia in deep waters of moderately eutrophic marine lakes, Island of Mljet, eastern Adriatic Sea

Hrustić, Enis; Bobanović-Ćolić, Svjetlana

doi:10.3989/scimar.04523.25a

Cited by 6 publications

(3 citation statements)

References 64 publications

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“…The NW Mljet coast is exposed to waves generated by the NE wind (bora), S wind (sirocco), and NW wind (mistral). Detailed information on the M area investigated is available in Bralić (1990), Bognar & Curić (1995), Riđanović & Šimunović (1995), Benović et al (2000), Zavodnik (2003), Dell'Angelo & Zavodnik (2004, Kružić et al (2008), and Hrustić & Bobanović-Ćolić (2017). The Dubrovnik site (D) is located two miles SE from the Old Town.…”

Section: Study Areamentioning

confidence: 99%

Epilithic diatom communities from areas of invasive Caulerpa species (Caulerpa taxifolia and Caulerpa cylindracea) in the Adriatic Sea, NE Mediterranean

et al. 2019

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Epilithic diatom community structures are compared among three locations of the eastern Adriatic Sea coast (Croatia), in the presence of two different invasive Caulerpa species, C. taxifolia and C. cylindracea, which have spread rapidly in the Mediterranean in the last decades. Forty samples were taken seasonally at three sites (island of Hvar, island of Mljet, and Dubrovnik) between November 2008 and October 2010. Light and electron microscopy examinations were used for qualitative analysis. Altogether 310 epilithic taxa belonging to 65 genera were identified. The highest number of these taxa belonged to Mastogloia (48) and Amphora (32), followed by Diploneis (24), Nitzschia (23), Navicula (22), and Cocconeis (19). A similar seasonal shift in growth form structure was observed for epilithic communities at the three sampling sites, where the number of erect group diatoms doubled (Hvar, Mljet) and tripled (Dubrovnik) in spring. Apart from erect forms, Dubrovnik and Mljet were characterised by adnate forms, while Hvar was characterised by tube-dwelling forms. The highest values of the Shannon-Wiener Diversity Index were recorded in autumn and ranged from 5.26 to 5.34. ANOSIM tests performed on species relative abundance data confirmed that the diatom communities differed significantly between the sampling sites, and that the differences were correlated with the presence of the two species of invasive macroalgae (Hvar – area of C. taxifolia; Mljet and Dubrovnik – areas of C. cylindracea). As revealed by SIMPER analyses, the group of taxa contributing the most to variance between diatom assemblages from sites of different invasive alga included Cocconeis scutellum var. scutellum, Rhopalodia pacifica, Navicula ramosissima, and Berkeleya rutilans. Although the spatial variation in communities may also reflect the effects of unmeasured environmental variables, the results suggest the possible influence of invasive seaweeds of the genus Caulerpa which may affect the habitat by competing with autochthonous algae. This study contributes to the knowledge of diatom diversity both at regional and at broader scales in these challenged environments.

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Section: Study Areamentioning

confidence: 99%

Epilithic diatom communities from areas of invasive Caulerpa species (Caulerpa taxifolia and Caulerpa cylindracea) in the Adriatic Sea, NE Mediterranean

et al. 2019

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“…This is particularly critical in the Zaton Bay region, resulting in the frequent occurrence of phytoplankton bloom (Šupraha et al, ). Based on the example of KRE, SGD most likely plays a significant role for the nutrient budgets along the entire eastern coast of the Adriatic Sea where numerous karstic estuaries (Benac et al, ; Viličić et al, ) and marine lakes (Hrustić & Bobanović‐Ćolić, ; Wunsam et al, ) are under the influence of SGD.…”

Section: Discussionmentioning

confidence: 99%

Net Submarine Groundwater‐Derived Dissolved Inorganic Nutrients and Carbon Input to the Oligotrophic Stratified Karstic Estuary of the Krka River (Adriatic Sea, Croatia)

Liu

Hrustić

et al. 2019

JGR Oceans

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Submarine groundwater discharge (SGD) is a significant source of biogenic elements in estuaries, and relevant studies in karstic estuaries are scarce. Krka River Estuary (KRE), located on the eastern Adriatic Sea (Croatia), is a typical oligotrophic stratified karstic estuary. In this study, based on 226Ra and 228Ra, the total SGD flux into the KRE surface layer was estimated to be (12.8–16.2) × 105 m3/day. A conservative estimation of the fresh groundwater flux was (5.0–8.3) × 105 m3/day, which accounts for 10–17% of the Krka River discharge into the estuary. By establishing water and nutrient budgets in the KRE surface layer, we found that SGD dominated the nutrient sources, although it accounted for a small portion of the total inflow water. Specifically, net SGD‐derived dissolved inorganic nitrogen (DIN) and silicates contributed 58–90% and 24–64%, respectively, to the total input fluxes. These results indicate that SGD was a major external nutrient source, in which net SGD‐derived high DIN flux and high DIN to dissolved inorganic phosphorus ratio may affect productivity in the KRE ecosystem and nearby Adriatic Sea. Additionally, net SGD‐derived dissolved inorganic carbon (DIC) flux in the KRE (1.53 mol · m2 · day) was much higher than those in most estuaries worldwide, suggesting that the DIC‐enriched karst aquifers are important sources for global carbon cycle. Therefore, the impact of net SGD‐derived DIC from karst aquifers on coastal seas will likely become more evident and substantial with further development of global climate change, such as sea level rise.

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“…This alternative has proved effective in other similar systems. For example, in the National Park Mljet in Croatia, the widening of the Soline channel had a very positive impact: the disappearance of anoxia in the near-sediment waters of the most inner part of the system (Hrustić and Bobanović-Ćolić 2017). Because of the choked nature of the lagoon, the Cuban government is at present building a flushing system driven by wave and tide oscillations that is designed specifically to clean up coastal lagoons (Alatorre-Mendieta et al 2004).…”

Section: Discussionmentioning

confidence: 99%

Coexisting ecosystem states in a tropical coastal lagoon under progressive eutrophication in the northern Cuban keys

et al. 2018

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Through a nested suite of methods here we contrast the coexistence of different ecosystem states in a tropical coastal lagoon, the Laguna Larga, with increasing eutrophication stress between 2007 and 2009. Water temperature averaged 27.4°C in the lagoon and showed a slight positive trend during the study period. Salinity averaged 35.0±6.2, exhibiting high spatial and temporal variability, and also a slight positive trend in time. In contrast, dissolved oxygen showed a substantial decreasing trend (–0.83 ml L–1 y–1; –13.3% y–1) over the period, while nutrients increased dramatically, particularly total phosphorus (2.6 µM y–1), in both cases sustaining the progression of eutrophication in the lagoon during the three years we sampled. The Karydis nutrient load-based trophic index showed that the lagoon has a spatial pattern of increasing eutrophication from the sea and the outer sector (oligotrophic-mesotrophic) to the central (mesotrophic) and the inner sector (mesotrophic-eutrophic). Two ecosystem states were found within the lagoon. In the outer oligotrophic sector, the dominant primary producers were macroalgae, seagrasses and benthic diatoms, while mollusc assemblages were highly diverse. In the inner and central sectors (where trophic status increased toward the inner lagoon) a phytoplankton-dominated ecosystem was found where mollusc assemblages are less diverse. In spite of the progression of eutrophication in the lagoon, these two different ecosystems coexisted and remained unchanged during the study period. Apparently, the effect of water residence time, which increases dramatically toward the inner lagoon, dominated over that of nutrient loadings, which is relatively more homogeneously distributed along the lagoon. Therefore, we consider that actions that reduce the water residence time are likely the most effective management options for this and other similarly choked lagoons.

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Hypoxia in deep waters of moderately eutrophic marine lakes, Island of Mljet, eastern Adriatic Sea

Cited by 6 publications

References 64 publications

Epilithic diatom communities from areas of invasive Caulerpa species (Caulerpa taxifolia and Caulerpa cylindracea) in the Adriatic Sea, NE Mediterranean

Epilithic diatom communities from areas of invasive Caulerpa species (Caulerpa taxifolia and Caulerpa cylindracea) in the Adriatic Sea, NE Mediterranean

Net Submarine Groundwater‐Derived Dissolved Inorganic Nutrients and Carbon Input to the Oligotrophic Stratified Karstic Estuary of the Krka River (Adriatic Sea, Croatia)

Coexisting ecosystem states in a tropical coastal lagoon under progressive eutrophication in the northern Cuban keys

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