QUANTIFICATION OF FLOATING MARINE MACRO LITTER

Session Chairs: Georg Hanke, European Commission Joint Research Centre Directorate D Sustainable Resources; Stefano Aliani, CNR-ISMAR, Institute of Marine Science, Italy

This session focuses on quantification of floating macro litter/debris at sea through development of harmonized approaches.

Floating Marine Macro Litter (debris) FMML has been spotted in all marine areas on the planet, sometimes with remarkable abundances. Its presence is posing an increasing thread to the marine environment and human activities. FMML has also direct negative impact on wildlife such as seabirds, fish, turtles and marine mammals through ingestion or entanglement. Through complex degradation processes floating macro litter is the source for secondary microparticles in the marine environment. Floating litter can end up on the sea shores, thus affecting tourism and animals on beaches.

The availability of georeferenced, detailed data of appropriate quality is of basic importance for tackling the marine litter problem, also because the proper assessment of the quantities of Litter and the relative distribution at sea provide the exposure information for risk assessments.

At present, information mainly rely on human visual sightings, but data from different groups or different geographic regions are often not comparable because a full harmonization of approaches is still lacking. Therefore, the use of agreed or comparable protocols, item lists and tools is the way forward towards the acquisition of data which can be used across regions for the deriving trends of litter pollution.

This session will present and discuss the current state of macrolitter monitoring to pave the way towards international agreed protocols. It will be a platform for the presentation of results from monitoring at different spatial scales and from different marine areas. It will thus provide information about levels and gradients of pollution and will propose examples of the currently-applied methodologies.

 

Abstracts

 

Estimating the abundance of floating plastics at sea – lessons from beach surveys

presenting: Peter Ryan (FitzPatrick Institute of African Ornithology, South Africa); authors: Peter Ryan (FitzPatrick Institute of African Ornithology, South Africa), Coleen Moloney (Marine Research Institute)

The density of floating plastics and other anthropogenic debris is notoriously variable at local scales, linked to convergence zones. Dispersal and dispersion of floating items is further influenced differentially by currents and winds, depending on the buoyancy of the items. As a result, estimating the abundance of floating plastics at sea is a non-trivial exercise, requiring large sample sizes if the goal is to detect spatial or temporal differences in debris abundance. Sampling strategies also have to take cognisance of the wide range of sizes of marine debris, and be structured accordingly. We attempted to estimate the entire population of plastic items stranded on a remote South African beach, using a variety of sampling approaches to capture macro-, meso- and microplastics, both on the beach surface and buried to a depth of 150 mm. This revealed highly contrasting patterns between the abundance and mass of debris; more than 99% of plastic items were <5 mm, but these accounted for only 2% of the total mass of plastics. Among macroplastic items, only 25% were visible at the beach surface, but most of the buried items were small, accounting for only 7% of the total mass of plastics. These differences between mass and number would be even more extreme if we had expanded our macro-litter sampling sufficiently to capture a representative sample of megaplastic items. Comprehensive data for floating plastics at sea are not available, but indications from various studies suggest that similar patterns exist. Accordingly, it is important to sample the full size spectrum of floating debris, using tools ranging from bulk water sampling (microplastics), neuston nets (mesoplastics) and direct observations (macroplastics). Adequate sampling of sub-surface plastics, especially macro litter, poses a significant challenge.

 

Monitoring the abundance of floating macro-debris in the marine environment: a comparison between distance sampling and fixed-width strip-transect techniques

presenting: Giuseppe Suaria (CNR-ISMAR, Italy); authors: Giuseppe Suaria (CNR-ISMAR, Italy), Andrea Pierucci (Università degli Studi di Cagliari), Veronica Padula (University of Alaska), Stefano Aliani (CNR-ISMAR), Peter Ryan (FitzPatrick Institute of African Ornithology)

Ship-based visual surveys are a powerful and inexpensive tool to monitor the abundance of floating macro-litter (FML) in the marine environment, however the comparison among different studies is often hampered by substantial differences in counting techniques. At present, two main methods are commonly used: distance sampling (line-transect) and fixed-width strip-transects, although the efficacy of these two protocols has never been compared in the field. We report the results of a comparison exercise carried out during the Antarctic Circumnavigation Expedition (ACE) and along a latitudinal gradient in the eastern Atlantic Ocean onboard the R/V Akademik Tryoshnikov which sailed from Bremerhaven (Germany) to Cape Town (South Africa) in Nov-Dec 2016, circumnavigated the Antarctic continent and sailed back to Bremerhaven in Mar-Apr 2017. A total of 301 half-an-hour transects were performed in parallel by two different observers. During each transect the number of floating objects was recorded independently by both observer using one of the two techniques. The densities of FML were then computed for each transect according to both methods and the results were compared across a wide range of litter concentrations. Preliminary results suggest that the method to be chosen will mainly depend on the local abundance of floating litter, as the performance of distance sampling techniques seems to decrease in high-concentration areas, while the strip-transect method appear less effective in detecting floating items in low-concentration areas, such as the Southern Ocean. This information provides a valuable contribution to the urgent need of standardized monitoring protocols, which is paramount for a better understanding of temporal and spatial patterns in the off-shore distribution of floating marine debris.

 

Settings methodologies for monitoring floating marine macro litter: the MEDSEALITTER effort

presenting: Antonella Arcangeli (ISPRA, Italy); authors: Antonella Arcangeli (ISPRA, Italy), Fabrizio Atzori (Capo Carbonara MPA), Asuncion Borrell (University of Barcelona), Gaëlle Darmon (Cnrs-cefe), Léa David (EcoOcean Institut), Nathalie Di Meglio (EcoOcean Institut), Stefania Di Vito (Legambiente), Natalia Fraija-Fernández (University of Valencia), Antonio Raga Juan (University of Valencia), Morgana Vighi (University of Barcelona)

Although the Mediterranean Sea is one of the largest biodiversity hotspots, it is also one of the most polluted seas worldwide. Concentrations of floating litter in the Mediterranean Sea are suspected to be very high, though current data do not allow yet their complete assessment and the identification of sources and accumulation areas.

In this context, a priority issue is the development of widely agreed standardized monitoring protocols to be implemented under the Marine Strategy Framework Directive, supporting Marine Protected Areas (MPA).

MEDSEALITTER project is actively investigating methodologies for monitoring floating marine macro litter. The approach aims at networking representative MPAs, scientific organizations and environmental NGOs for developing and testing efficient and cost-effective protocols to monitor and manage litter impact on biodiversity. Different experimental designs were conducted to implement protocols at two spatial scales: i) in pilot large scale areas, using synoptic surveys from ferries; ii) in pilot MPAs, using a) visual surveys conducted from commercial vessels, sailing vessels and aircrafts and b) analyses of automated photographs obtained from aircrafts and drones surveys. Results allowed a comprehensive assessment of the effect of various observation parameters on the sighting probability of floating marine litter. Overall, the accurate determination of the settings needed to draft consistent monitoring protocols will take into account spatial scale surveillance, type of survey (visual/automatic), detectability and platform used.

The common protocol will be tested in 2018 in pilot areas representing various Mediterranean ecological environments.

 

Floating marine macro litter monitoring in the Black Sea: EMBLAS II experience.

presenting: Maria Pogojeva (State Oceanographic Institute, Moscow,  Russia); authors: Maria Pogojeva (SOI, Russia), G. Hanke (EC Joint Research Centre, Italy),  D. Gonzalez (EC Joint Research Centre, Italy), O. Savenko (Ukrainian Center of Ecology of the Sea, Ukraine), I.Tretiak (Ukrainian Center of Ecology of the Sea, Ukraine), Y. Kotelnikova (Ukrainian Center of Ecology of the Sea, Ukraine), N. Machitadze (Iv. Javakhishvili Tbilisi State University Al. Janelidze Institute of Geology,  Georgia), N. Gelashvili (Iv. Javakhishvili Tbilisi State University Al. Janelidze Institute of Geology,  Georgia), V. Gvakharia  (Iv. Javakhishvili Tbilisi State University Al. Janelidze Institute of Geology,  Georgia),  K. Bilashvili (Iv. Javakhishvili Tbilisi State University, Georgia), V. Trapaidz (Iv. Javakhishvili Tbilisi State University, Georgia)

Floating macro litter is the fraction of marine litter to which marine wildlife is directly exposed at sea, potentially leading to ingestion and entanglement. Litter floating in the sea surface is therefore part of the assessment criteria under the EU Marine Strategy Framework Directive.

In the frame of the EMBLAS II project (‘Improving environmental monitoring in the Black Sea’) basin-crossing multinational exploration surveys (Joint Open Sea Surveys, JOSS), specific national surveys (National Pilot monitoring Studies, NPMS) and surveys from ships-of-opportunity, all including opportunistic monitoring of floating litter, were performed during 2016-2017 in the Black Sea. The surveys involved scientists from Georgia, Russia and Ukraine, while scientists from Romania, Bulgaria and Turkey participated to accompanying workshops and training.

As methodologies for monitoring of floating macro litter are still under development, the EMBLAS II surveys provided opportunities for discussion, testing approaches and contributing to the further development of the monitoring tools. The harmonization of monitoring and the providing of guidance is essential, as operationally defined parameters are being quantified. Litter was monitored during the EMBLASS II surveys by trained observers, acquiring georeferenced data through a tablet computer application, developed by JRC.

The presented observations results have been acquired on multiple surveys, covering both coastal waters in Ukraine, Russia, Georgia and the open Black Sea. Concentrations of floating macro litter were found to be highly variable, ranging from ca. 20 items/km² to above 300 items/km². These first basin wide results contribute to a holistic assessment of marine litter and the assessment of the environmental state of the Black Sea.

 

Modeling incidental marine debris bycatch in the Hawaii-based pelagic longline fishery

presenting: Amy Uhrin (NOAA Marine Debris Program, United States); authors: Amy Uhrin (NOAA Marine Debris Program, United States), Jon Brodziak (NOAA Pacific Islands Fisheries Science Center), William Walsh

The remoteness of the North Pacific Ocean hampers at-sea detection and removal of marine debris. Commercial longline fishing gear, with its array of suspended hooks, can snag marine debris and may provide an opportunity to assess floating and mid-water marine debris abundance and distribution at a regional scale. Observations of species-specific catch and other operational details from vessels participating in the Hawaii-based pelagic longline fishery were initiated in 1994 as part of NOAA’s Pacific Islands Regional Observer Program. In 2007, onboard observers began additionally recording longline encounters with marine debris. We used an existing zero-inflated negative binomial model developed for standardizing catch-per-unit effort (CPUE) of bycatch species to explore incidental “catches” of marine debris in this fishery from data spanning 2008-2016. Data collected from 128 vessels (457 trips) yielded 966 marine debris encounters dominated by derelict nets and associated gear from other fisheries. Mean CPUE (catch per 1000 hooks) for marine debris was four times greater in the shallow-set sector of the fishery (targeting primarily swordfish) versus the deep-set sector (targeting primarily bigeye tuna). There was no temporal trend in debris CPUE but CPUE was higher at higher latitudes. There was a significant effect of observer experience; observers averaging 2.5 years of experience prior to 2008 reported more debris than observers with less experience. Marine debris observations from the Hawaii-based pelagic longline fishery can provide an opportunistic, yet regular, mechanism for assessing the distribution and abundance of derelict fishing gear. Some longline fishermen voluntarily haul snagged debris from the ocean. Thus, incentivizing at-sea removal may elicit further cooperation.