Kū Hou Kuapā: Cultural Restoration Improves Water Budget and Water Quality Dynamics in Heʻeia Fishpond

Abstract

In Hawaiʻi, the transition from customary subsistence flooded taro agroecosystems, which regulate stream discharge rate trapping sediment and nutrients, to a plantation-style economy (c. the 1840s) led to nearshore sediment deposition—smothering coral reefs and destroying adjacent coastal fisheries and customary fishpond mariculture. To mitigate sediment transport, Rhizophora mangle was introduced in estuaries across Hawaiʻi (c. 1902) further altering fishpond ecosystems. Here, we examine the impact of cultural restoration between 2012–2018 at Heʻeia Fishpond, a 600–800-year-old walled fishpond. Fishpond water quality was assessed by calculating water exchange rates, residence times, salinity distribution, and abundance of microbial indicators prior to and after restoration. We hypothesized that R. mangle removal and concomitant reconstruction of sluice gates would increase mixing and decrease bacterial indicator abundance in the fishpond. We find that Heʻeia Fishpond’s physical environment is primarily tidally driven; wind forcing and river water volume flux are secondary drivers. Post-restoration, two sluice gates in the northeastern region account for >80% of relative water volume flux in the fishpond. Increase in water volume flux exchange rates during spring and neap tide and shorter minimum water residence time corresponded with the reconstruction of a partially obstructed 56 m gap together with the installation of an additional sluice gate in the fishpond wall. Lower mean salinities post-restoration suggests that increased freshwater water volume influx due to R. mangle removal. Spatial distribution of microbial bio-indicator species was inversely correlated with salinity. Average abundance of Enterococcus and Bacteroidales did not significantly change after restoration efforts, however, average abundance of a biomarker specific to birds nesting in the mangroves decreased significantly after restoration. This study demonstrates the positive impact of biocultural restoration regimes on water volume flux into and out of the fishpond, as well as water quality parameters, encouraging the prospect of revitalizing this and other culturally and economically significant sites for sustainable aquaculture in the future.

Hawai‘i in Focus: Navigating Pathways in Global Biocultural Leadership

“…An important contribution by Kealiikanakaoleohaililani et al [17] highlights the spiritual foundations and the role of ritual in biocultural restoration in indigenous places. The issue also includes papers that quantify ecosystem services and cultural services that are the products of biocultural restoration, including flooded field systems [33], agroforestry systems [34], and aquaculture systems [35].…”

Reconnecting Rural Native Hawaiian Families to Food through Aquaponics

“…Moku are further divided into ahupua'a, which typically extend from the uplands all the way down onto the reefs and into the sea (Kame'eleihiwa 2016). The health and aquaculture production of an ahupua'a's reefs and coastal fisheries, including loko i'a (fishponds), are directly tied to the health of its lo'i kalo (flooded taro agroecosystems) and upland forestry areas (Möhlenkamp et al 2018). As a result, there was an understanding that kānaka (people) have the kuleana (responsibility) to maintain the health of each part of the ahupua'a, ensuring the pono and lōkahi of the entire system.…”

Coral Resilience at Malauka`a Fringing Reef, Kāneʻohe Bay, Oʻahu after 18 years

“…The study site was a 600-meter section of the Malauka'a fringing reef ( [26]. The southern end of the reef is subjected to freshwater stream and pond output from He'eia stream and a triple mākāhā (sluice gate) within Paepae o He'eia [27]. The selected reef suffered bleaching and low mortality (<5%) during the 2014/2015 bleaching event [11].…”

“…Increased freshwater input onto the southern portion of the surveyed reef may have impacted the abundance of P. damicornis. Following biocultural restoration of the Paepae o He'eia, water exchange between the fishpond and the adjacent reef increased, with an additional 14,418 m 3 of pond water being flushed out onto the reef during each ebb tidal cycle [27].…”