• Views from Penobscot Mountain summit.


    National Park Maine

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  • Carriage Roads to reopen

    All park carriage roads will reopen to foot traffic only on Friday, 4/25. Bikes & horses are not permitted at this time to prevent damage during the spring thaw. Use caution as seasonal repairs are not completed. For more info: 207-288-3338.

  • Trail Closures: Peregrine Falcon Nesting

    Precipice Cliff and Valley Cove areas are closed to all public entry until further notice for peregrine falcon nesting season. More »

  • Blackwoods Campground is open

    Blackwoods Campground is open and is sites are available by self-registration at the campground. More »

  • 2014 Season Openings

    Park Loop Rd, Cadillac Mountain Rd, & Hulls Cove Visitor Center is open. Call (207) 288-3338 or follow us on Facebook (www.facebook.com/AcadiaNPS) for more information More »

  • Jordan Pond boat ramp parking lot is closed for construction

    It's scheduled to reopen on June 28. There may be intermittent openings at the discretion of the contractor. The North Lot parking area will remain open for access to the Jordan Pond House Restaurant & hiking & biking trails.

Field Guide to Algae - Green Algae

Acrosiphonia arcta in habitat - bright green on rock

Acrosiphonia arcta
This alga grows as a tufted mat in the lower intertidal zone. It looks unusually fuzzy because it has hooked filaments (see microscopic photograph). This alga is a favorite place for small crustaceans to hide to escape drying stress at low tide. Present winter–summer.

Photos by Joseph Stachelek.

Chaetomorpha melagonium growing vertically

Chaetomorpha melagonium
Chaetomorpha melagonium grows as a thick, beaded tube. The cells are so large that you can see them with your naked eye. Found in tide pools in the lower intertidal zone. Present winter–summer.

Photos by Joseph Stachelek.

Prasiola stipitata growing on rocks

Prasiola stipitata
Prasiola stipitata forms a short green turf (< 1 cm, see microcropic photograph) near bird droppings (an excellent source of nutrients) in the upper intertidal zone. Small, individual blades curve like a mouse ear. Present spring–summer.

Photos by Susan Brawley (left) and Sarah Hall (pop-up).

Ulothrix laetevirens along shoreline

Ulothrix laetevirens
Ulothrix laetevirens forms slippery, dark-green patches on rocks in the upper intertidal zone. Individuals that make up the patches are unbranched filaments. There is a single, band-shaped chloroplast in each cell (see microscopic photograph). Herds of herbivorous periwinkle snails feed at the edge of patches in spring and work their way inward until the patch disappears. Present winter–early summer.

Photos by Sarah Hall.

Ulva lactuca growing along shore

Ulva lactuca
“Sea lettuce” is a flat blade (two cell layers thick) that grows up to 20 cm long. This bright to dark-green sea vegetable is consumed by many invertebrates and also by humans in soups and salads. Blades that have upper white sections have just released reproductive cells; this occurs most often near full and new moons, just after dawn. Ulva lactuca is found in tide pools and in the lower intertidal zone. Present year round, but most abundant in summer–fall.

Photos by Susan Brawley (left) and Sarah Hall (pop-up).

Ulva intestinalis growing in tidepool

Ulva intestinalis
This alga tolerates low salinity and is found in the upper intertidal zone in pools and areas of runoff. Young individuals are slender blades, whereas older individuals form a tube. Gas bubbles accumulate inside the tube and make it float. Gametes and zoospores are released shortly after dawn near new and full moons. Individuals that have released reproductive cells turn white.

Photos by Joseph Stachelek (left) and Sarah Hall (pop-up).

Did You Know?

Image of the Guide's Guide cover

The Guide's Guide to Acadia National Park, originally created to share important information about the park's facilities and natural and cultural resources with commercial guides, is available to the public on this website. The guide contains everything you would want to know about the park. More...