Beach Sampling

Plastics in Palau

Rapid Assessment of Shoreline Debris in a Remote Western Pacific Island

Visible Debris

R.C. Ritter, P.A. Ritter

Introduction:

The rise of synthetic plastics in consumer and industrial use has been matched with an increasing challenge to their effective post-life disposal and containment. Unfortunately, significant, and increasing amounts of these materials find their way downstream to marine waters. This is driven by their durability, persistence and buoyancy making them natural candidates for long-term accumulation. Their presence creates a number of significant threats to the marine environment, well characterized by Moore (2008). These include:

  1. Aesthetic impact to valuable beaches and near shore waters impacting tourism profits
  2. Entanglement of both pelagic life (seals, fish, whales) and fragile benthic life (corals)
  3. Ingestion by marine life both macro and planktonic including the now well known and gruesome affect on pelagic seabirds like albatross
  4. Collateral affects including transport of species and release of harmful chemicals

Due to the endurance of these materials, rapid increases in global commerce and effective global oceanic circulation, such debris are being spread far beyond the source. An important part of resolving these issues is improved local understanding and engagement in the presence of marine plastic debris. The purpose of this work was to test a simple walking transectmethod of sampling larger debris in an area that would normally be considered pristine.

 

Methods:

The beach assessment was carried out on Republic of Palau on 26 May 2008. We selected a section of shoreline on the inshore side of the island (approx N7 02 / W 134).  A 317m stretch of beach was sampled at low tide. Transect width was defined as waters edge to within 2m beyond sands edge on the up-shore side. Average transect width was estimated with multiple measurements along the path- facilitated by a fairly consistent beach shape. An observer (RR) walked the transect length counting and classifying all visible debris into six easily identified types:

  1. Plastic bottle including both beverage and other such as bleach
  2. Fishing gear including nets, lines, floats
  3. Plastic bags
  4. Other plastic covering a wide range of fragments
  5. Al Cans
  6. Other non-plastic including polystyrene foams

Results were summarized and then calculated as totals by type for the transect. Rough extrapolation for the whole of Peleliu Island was done with a shoreline length estimate developed using Google Earth. Physical visits were made to the south and eastern shorelines to visually confirm similar levels of deposition.

 

Results

Summarized results are as follows:

 

Debris Type Transect Count Density in units/ m2 Density in linear meters of beach / unit Island extrapolation number
Plastic Bottle

55

.009

5.8

4,187

Fishing Gear

28

.005

11.3

2,131

Plastic Bags

17

.003

18.6

1,294

Other Plastic

101

.017

3.1

7,688

Al Cans

11

.002

28.8

837

Other non-plastic

11

.002

28.8

837

All Total

223

.037

1.4

16,975

 

Visual breakdown of the transect sample by type:
Photo samples of more striking debris include hermit crab employing a modern shell of plastic and overview of beach debris:

The sampling method proved easy to set up and complete, requiring nothing more than a clip board and ability to measure out distances in a very rough order manageable with foot pacing and verification of average stride length. Analysis was done in a simple Excel spreadsheet and the use of distance mapping on Google Earth.

Summary:

Marine plastics and other human sourced debris are a remarkably pervasive, and increasing presence in the worlds oceans. This carries significant known, and likely poorly understood threats to our use of the oceans, and to the vital health of these environments. Unfortunately, a remote, world renowned, pristine site like Palau now has beaches with approximately one piece of visible debris per 1.5mwith a total potentially as above 15,000 pieces on the island. This is surprising, inconsistent with the sense of remote and pristine, and does not bode well for the long-term welfare of the island.

This sampling method clearly is a rough-and-ready method that should only be taken as a relative indicator. Its value however, lies not in accuracy, but in applicability and speed. Un-trained professionals schoolchildren, families, business operators, fisherman or lightly resourced environmental authorities can easily replicate this method. The transect size and width can be relatively flexible, allowing this to be adapted to level of resources and local topography. This simple method should have value as a teaching, awareness and rough trend-monitoring tool.

 

References:

Moore, C.J. 2008: Synthetic polymers in the marine environment: a rapidly increasing long-term threat. Environmental Research 108(2008): 131-139