Universita' di Trieste - Marine Biology Station Piran

Restoration Project

Universita' di Trieste - Marine Biology Station Piran

Restoration Objective:

In this context, the objectives of this study were (1) to analyse the reproductive traits of three populations of G. barbata from three nearby donor sites (i.e., Izola, Strunjan, Piran) in order to assess the differences in their reproductive potential and reproductive success, and (2) to evaluate the restoration success in relation to the different donor and receiving sites (Miramare MPA vs. Marine Biology Station Piran) and the methods used. The added value of our work is that by combining two methods, for the first time different donor and receiving sites were compared in terms of restoration success of G. barbata.

Site Selection Criteria:

The coastal area off the Marine Biology Station Piran (hereafter MBSP) in Slovenia (45.5177, 13.5680), where less than a decade ago there was a dense brown algal forest consisting mainly of G. barbata and C. compressa. This habitat was completely destroyed in 2016 due to invasive encroachment for beach construction, when no precautions were taken to limit environmental damage. This site is also affected by fish grazing pressure (Orlando-Bonaca et al., 2021b).

Cause Of Decline:

A sharp decline of Fucales has also been reported in the northern Adriatic basin (Falace et al., 2010; Orlando-Bonaca and Rotter, 2018; Orlando-Bonaca et al., 2021a), leading to displacement by turf-forming taxa in shallow waters. The occurrence of these low-lying algae is likely related to human induced hydromorphological changes to the shoreline and high sediment resuspension rates (Falace et al., 2010; Orlando Bonaca and Rotter, 2018) rather than nutrient enrichment, as the northern Adriatic is considered oligotrophic (Mozetič et al., 2012).

Key Reasons For Decline:

Multiple

Scientific Paper

Where and how-new insight for brown algal forest restoration in the Adriatic

Orlando-Bonaca, M., Savonitto, G., Asnaghi, V., Trkov, D., Pitacco, V., Šiško, M., ... & Falace, A. (2022).https://ricerca.ogs.it/retrie...c3cfaf82/fmars-09-988584.pdf

Organisation:

Universita' di Trieste

Site Observations:

Observation Date

1st Jul 2021 – 1st Nov 2021

Action Summary:

Both hybrid (laboratory-based followed by suspended aquaculture) and ex situ (laboratory-based only) recruitment of Gongolaria barbata, collected from different donor sites, was conducted prior to transplantation to the restoration sites, where the juveniles were monitored for approximately half a year.

Apices with mature receptacles collected from 1–2 m depth at donor sites were placed on clay tiles within aerated aquaria containing 0.22 μm-filtered seawater and cultivated for 2 weeks prior to being transported to the receiving sites, where they were fixed to plastic lantern nets (55 cm diameter) suspended at 2 m depth and held for 3 months.

The tiles were then transplanted to the rocky bottom of the restoration site and attached with screws to preassembled outplanting modules consisting of 50 × 50 cm concrete plates covered with iron anti-grazing cages (mesh size 1 × 1 cm²) and secured with metal wedges.

Lessons Learned:

Restoration success was strongly influenced by both donor-site characteristics and receiving-site environmental conditions. Juveniles sourced from high-sediment environments performed better under similar sediment resuspension conditions, suggesting local environmental adaptation. The hybrid method successfully reduced laboratory cultivation time and performed well under favourable conditions, but was highly sensitive to environmental disturbances such as blooms and biofouling during the suspended-culture phase.

Project Outcomes:

The success of outplanting juveniles in the field was highly variable and depended on both the location of the donor/ receiving sites and the outplanting method. As with the ex situ method, the greatest differences in Slovenia (MBSP) were due to the different donor sites. For the hybrid method, the main differences were due to the receiving site: the method performed much better at MBSP than at Miramare (Figure 8). As this method performed better at Miramare in 2019 (Savonitto et al., 2021), these poorer results could be related to a series of unfavourable environmental conditions that occurred in the Italian part of the Gulf of Trieste in spring and early summer 2021.

Nature of Disturbance:

An impressive bloom of the jellyfish Rhizostoma pulmo, followed by a massive bloom of Noctiluca scintillans, which was much more pronounced in the Italian waters than in the Slovenian ones (ARPA FVG, 2021), characterised the area during the laying of the tiles on the lantern nets and in the following crucial weeks. In addition, the tiles on the lantern nets were colonised by mussel and oyster recruits from June onwards, and this trend intensified in July (i.e., at the time of outplanting on the sea bottom), favoured by a mussel farm near the MPA that probably served as a larval source. Thus, the molluscs probably displaced the G. barbata seedlings.

Area of Restoration (Ha)

0.00008

Distance to nearest kelp forest (in metres)

2,500

Indicator Data:

Indicator:

Ending Value:

Starting Value:

Percent Survival

74.6600
%
100.0000
%
Transplant Info:
Life Stage:Juveniles
Source:Culture

Observation Date

7th May 2021 – 1st Nov 2021

Action Summary:

Both hybrid (laboratory-based followed by suspended aquaculture) and ex situ (laboratory-based only) recruitment of Gongolaria barbata, collected from different donor sites, was conducted prior to transplantation to the restoration sites, where the juveniles were monitored for approximately half a year.

Apices with mature receptacles collected from 1–2 m depth at donor sites were placed on clay tiles within aerated aquaria containing 0.22 μm-filtered seawater and cultivated for 4 weeks under controlled conditions (15°C temperature, 125 mmol m⁻² s⁻¹ light intensity, and a 15:9 h light:dark cycle).

The tiles were then transplanted to the rocky bottom of the restoration site and attached with screws to preassembled outplanting modules consisting of 50 × 50 cm concrete plates covered with iron anti-grazing cages (mesh size 1 × 1 cm²) and secured with metal wedges.

Lessons Learned:

Restoration success was strongly influenced by both donor-site characteristics and receiving-site environmental conditions. Juveniles sourced from high-sediment environments performed better under similar sediment resuspension conditions, suggesting local environmental adaptation. The hybrid method successfully reduced laboratory cultivation time and performed well under favourable conditions, but was highly sensitive to environmental disturbances such as blooms and biofouling during the suspended-culture phase.

Project Outcomes:

The success of outplanting juveniles in the field was highly variable and depended on both the location of the donor/ receiving sites and the outplanting method. As with the ex situ method, the greatest differences in Slovenia (MBSP) were due to the different donor sites. For the hybrid method, the main differences were due to the receiving site: the method performed much better at MBSP than at Miramare (Figure 8). As this method performed better at Miramare in 2019 (Savonitto et al., 2021), these poorer results could be related to a series of unfavourable environmental conditions that occurred in the Italian part of the Gulf of Trieste in spring and early summer 2021.

Nature of Disturbance:

An impressive bloom of the jellyfish Rhizostoma pulmo, followed by a massive bloom of Noctiluca scintillans, which was much more pronounced in the Italian waters than in the Slovenian ones (ARPA FVG, 2021), characterised the area during the laying of the tiles on the lantern nets and in the following crucial weeks. In addition, the tiles on the lantern nets were colonised by mussel and oyster recruits from June onwards, and this trend intensified in July (i.e., at the time of outplanting on the sea bottom), favoured by a mussel farm near the MPA that probably served as a larval source. Thus, the molluscs probably displaced the G. barbata seedlings.

Area of Restoration (Ha)

0.00009

Distance to nearest kelp forest (in metres)

2,500

Indicator Data:

Indicator:

Ending Value:

Starting Value:

Percent Survival

73.8200
%
100.0000
%
Transplant Info:
Life Stage:Juveniles
Source:Culture
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