Day 4 Survey of the Merrimack River Estuary

Day 4 Reflection


Top of Olde Town Hill looking toward Plum Island

Today was the final day of the four. I will say to all that read this blog that if you like the outdoors, prefer instruction that is a bit less facts centered, and sponsors and inspires creativity, Boat Camp for graduate credit is the place to go. Twice now I've had exposure to some incredible places that have clearly helped me develop real usable lessons for my class and had some fun too.

Weather condition were cool and very windy so we again began at the boat house for discussion on the impact of fishing with nets on the marine environment. We were asked to design a net specific too a type of fish with basic materials from simple netting, string and play doe. From my perspective it was a great springboard into discussing the effects of commercial fishing practices have on the marine environment, particularly how net types can cause collateral damage to species that are not of commercial interest. The discussion wasn't anti fishing but was about intelligent designs of nets (or lack of) can be a major benefit or problem. The Gill net, for example is very destructive because it is suspended in the water at at varying depths potentially several miles long and many feet deep. All sorts of marine creature (mostly fish but may include dolphins) get hung-up in the net and are unable to escape even though again they have no commercial interest. Since they can't swim many can not get oxygen and suffocate to death. Also most are made of microfibers (plastics) and takes 600 years to decompose, if a net breaks free it can continually snag and harm fish for years, called a ghost net. However in contrast there are practices and net designs that minimize many issues. I've personally used seine nets, useful in estuaries, ponds and lakes, and have found them to be useful for study. Rob mentioned using them for capturing bait species such as sand lance. Historically I did find it interesting that the Native Americans may have designed and built the first Weir net, fashioned from tree stems, which is effective in capturing channel fish where tides rise and fall.

Top of Olde Town Hill/Fallen Trees

Gary and Rob designed a field exercise that gave us access to the marsh but importantly was sheltered from the high winds. I have used Olde Town Hill in the past for geology lessons on drumlins and barrier beach formation. The downed trees at the top covered a huge area was awesome from the perspective of the impact of winds coming off the water, specifically from the northest. It was stated the February storm brought wind over 80 mph. This is a great site for visually seeing the barrier beach, the Merrimach River and the Great Marshes. It puts in perspective the entire estuarine system. On the south side there was a trail that I was unaware of that lead out in to the salt marsh to the the Little River, which flows through the marsh and empties into the Parker River. Since I already use Old Town Hill for a field trip I am likely to use the marsh for discussion of the formation of peat, indigenous species and adaptations. If I can figure out a way to have students investigate the fact that the peat in the marsh has nearly no smell, in contrast to the mudflats that had a strong sulfur odor I'll bring samples back to the lab as an addition to the field excursion. The aerobic and anaerobic thing I get and believe the kid will also but to have the student figure out the basic biology of why one smells but not the other is the sticking point for this moment. I'm also going to steal Gary's question "why put a field in the middle of the forest?" for the purpose of discussion of the historical use and related changes over time.

Day 4 Log

The mouth of the Merrimack River is a lagoon, a surprise to me, which is the mouth of a river that is protected by a barrier island with a narrow opening. The Estuary includes the lagoon,marshes and associated creeks. It is the barrier beach that creates the lagoon. The Great Marsh (mentioned above) is the largest in all of New England and extends from Hampton,NH to Gloucester incorporating approximately 22,000 acres. The Low marsh is closest to the ocean and has the highest levels of salt and the high marshes ,further up river have the lowest levels of salt. All fauna and flora, including plankton must be adapted or tolerance to changing salt conditions. During storms and spring tides salt water can reach even the high marsh.

Little River and Marsh

Marsh are formed from mudflats were species of Spartina are able to take hold. Spartina patens (salt marsh hay) is less salt tolerant and found farthermost away from the river water were as Spartina alterinifora (cord grass) is closest to the water and can be frequently completely covered by the brackish water. It is mostly these plants, especially their roots, that decompose in the mud becoming peat. Peat is pasty, not particularly smelly and can be compressed by as mush as 50 %, you could feel it move when walking or jumping. Marshes are the most productive ecosystems on the planet, specifically in regard to biomass, potentially accumulating up to 2 to 3 feet per year.

Coffee Bean Snail

We did find lots Coffee Bean snails, a shrimp species on the peat, along with oyster shells with barnacles on them. A number of cedar trees on the margins of the marsh had numerous Cedar Apple Gall (a rusty-red fungus). Charlie netted, in his own trap, a half dozen mummichogs which are small fish of about 2 inches that can be used as bait. Also observed was one Redwing Black Bird. Birds were not generally observable because of the high winds. The only invasive species observed was Fragmites brought here from England during colonial time. The problem is that they out complete native species such as cat-and-nine tails dominating an area and are not digestible by most native species, not allowing the transfer of energy up the food chain. Greenheads, nasty biting flies locally, turns out that its only the female that bites. She bites a hole in the skin and laps the blood for the rich protein, however the normally large number of birds eat lots of these greenheads, an important food source for them. Yea for the birds!

Charlee's Trap

Humans have use the salt marsh extensively for the salt hay as animal feed, even cutting canal into the marsh for irrigation to increase productively. In Ireland peat is dried into bricks to burn as a fuel. Today the salt marsh are a Protected Bird Area however in colonial days bird hunting was common.