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Guide to Pressing Seaweed: Introduction
Step 2: Collect  Click here to buy the printed booklet version
Be prepared and be safe at the shore
Safety is the most important consideration when collecting at the shore. Waves and tides can be dangerous on almost any coastline. However, on a rocky shore, where seaweeds are most abundant, the rocks and algae themselves can present the greatest danger. Algae-covered rocks, including those at the high-tide line that are only covered in a black film of blue-green algae, are invariably slippery. In this environment, scrapes and falls are common. Hip boots offer relatively good footing as well as some protection for your ankles and legs, and diving gloves can offer some additional protection for your hands. On rocky shores, step between rocks, never on top of them, and don't be tempted to collect specimens out of safe reach. You can use a hook or net on a long handle to help catch drift. If using a boat or SCUBA, remember that some seaweeds are pretty effective at tangling up propellers and legs. Wherever you collect, protective clothing, sunblock, and sunglasses are a good idea.
Look for seaweed on rocky shores, piers, docks, and cast up on beaches
Although seaweeds can be found on almost any coast in the world, they are generally most abundant at rocky shores. Many species grow attached directly to firm substrates (like rocks) in shallow water. The seaweeds that grow in sandy substrates are generally less abundant and restricted to the tropics. In areas with a sandy bottom, seaweeds can be found attached to artificial substrates such as piers, docks, and jetties. Often the best places to collect seaweeds are areas where drift collects on the shore. In such places, large amounts of many species can be found (look here), but because seaweeds can decay quickly when out of water, the quality of drift specimens should be scrutinized. If you are collecting attached specimens, check a local tide chart and try to collect during a very low tide, when the most seaweed is within safe reach while wading. Wherever you are, check with local authorities about regulations before collecting, and stay out of sensitive marine habitats (for example, reefs in the tropics and eelgrass beds in the Northwest Atlantic). What you find can vary dramatically from location to location and season to season. When you arrive at a collection spot, begin by recording the date, location, and general conditions (nature of the substrate, general abundance of seaweeds, etc.).
Carefully select and collect specimens
When collecting, try to select only whole, intact, fresh specimens. Selecting whole specimens is important for identification purposes and to best represent the organism in general. Holdfasts, attachment structures which are root-like in the kelps, are often torn off of specimens found in drift, but are important diagnostic features. When collecting attached specimens, scrape them off of their substrate with a knife to keep any holdfasts intact (but collect crustose species still attached to their substrate when practical). Considering the size of your mounting paper, it's best to select small representatives of species that are relatively large. To ensure that your samples are fresh, only collect attached seaweeds or drift specimens that are clean and intact. The best (and first) indicator of freshness is usually your nose. At the shore, move collected specimens quickly to a bucket of cold, clear seawater out of direct sunlight. Use ice packs to keep the seawater cold in the summer, and remember to keep your bucket in a place where it won't be tipped over by waves. It's a good idea to keep small specimens in clear plastic bags, so that they can be easily found later. In addition, some species of Desmarestia need to be isolated, because they produce acid that can destroy other specimens in a bucket. Record notes on the specific locations of collected specimens ('in drift', 'attached to rock near the mean low-tide line, exposed to waves', 'attached to rockweed [Fucus sp.] near the high-tide line') to help identify them and to increase their potential scientific value. Be certain to collect only what you will be using, never collect the only attached representative of a particular species, and be mindful that there are many marine animals that look like plants. Bring a guide to local seashore creatures to help make preliminary identifications in the field.
Sort and clean your specimens
At the shore or back indoors, examine each specimen separately in a tray of seawater (a white tray is best) to prioritize what you want to press. As you go, carefully clean specimens by rinsing off sand and trimming off any unwanted shells, rocks, or epiphytes (other plants growing off of your specimen). Keep your specimens in fresh seawater, if available, and discard anything that you won't be pressing. To keep your best specimens fresh, it's important to keep them away from decaying specimens and other debris. For professional collections, consider fixing specimens in 3-5% buffered Formalin seawater, as recommended by the U.S. National Herbarium, rinsing fixed specimens thoroughly before pressing. Formalin is noxious and toxic and should only be used in a laboratory setting. See the National Herbarium's Guide for more details on the use of Formalin.
Identify your seaweed specimens before pressing
Before you press your specimens, try to identify them using a field guide or taxonomic key. Although specimens can be identified after they have been pressed, characteristics such as texture and many microscopic features can be harder to interpret after pressing. However, if at first you can't identify a specimen, pressing it is still one of the best ways to preserve it for later study when you have more time, a better field guide, or access to a microscope. Some species can only be properly identified by microscopic features, but such techniques are beyond the scope of this guide. Basic instructions on these techniques can be found in many books on the identification of seaweeds.
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